Please read the following page and provide a useful backtrace for this crash : http://techbase.kde.org/Development/Tutorials/Debugging/How_to_create_useful_crash_reports

Still present in kde 4.1.1 . Backtrace:

Application: Dolphin (dolphin), signal SIGABRT
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
[Thread debugging using libthread_db enabled]
[New Thread 0xb5f42720 (LWP 6804)]
[KCrash handler]
#6  0xb7f4c410 in __kernel_vsyscall ()
#7  0xb679b085 in raise () from /lib/tls/i686/cmov/libc.so.6
#8  0xb679ca01 in abort () from /lib/tls/i686/cmov/libc.so.6
#9  0xb75a0367 in qt_message_output (msgType=QtFatalMsg, 
    buf=0xbfde004c "ASSERT: \"d\" in file /build/buildd/kde4libs-4.1.1+really4.1.1/kdecore/util/ksharedptr.h, line 116") at global/qglobal.cpp:2061
#10 0xb75a0458 in qFatal (msg=0xb76e7498 "ASSERT: \"%s\" in file %s, line %d")
    at global/qglobal.cpp:2263
#11 0xb75a0505 in qt_assert (assertion=0xb7547eff "d", 
    file=0xb7547734 "/build/buildd/kde4libs-4.1.1+really4.1.1/kdecore/util/ksharedptr.h", line=116) at global/qglobal.cpp:1831
#12 0xb75109f0 in KSharedPtr<KMimeType>::operator-> (this=0xbfde2174)
    at /build/buildd/kde4libs-4.1.1+really4.1.1/kdecore/util/ksharedptr.h:116
#13 0xb752e6e4 in KFilePlacesModel::dropMimeData (this=0x8183e40, 
    data=0x8556908, action=Qt::MoveAction, row=-1, column=-1, 
    parent=@0xbfde21f4)
    at /build/buildd/kde4libs-4.1.1+really4.1.1/kfile/kfileplacesmodel.cpp:558
#14 0xb70d6c81 in QAbstractItemView::dropEvent (this=0x83e68e8, 
    event=0xbfde29bc) at itemviews/qabstractitemview.cpp:1812
#15 0xb7100a2e in QListView::dropEvent (this=0x83e68e8, event=0xbfde29bc)
    at itemviews/qlistview.cpp:935
#16 0xb753736a in KFilePlacesView::dropEvent (this=0x83e68e8, 
    event=0xbfde29bc)
    at /build/buildd/kde4libs-4.1.1+really4.1.1/kfile/kfileplacesview.cpp:602
#17 0xb6c6a742 in QWidget::event (this=0x83e68e8, event=0xbfde29bc)
    at kernel/qwidget.cpp:7199
#18 0xb6fa52a3 in QFrame::event (this=0x83e68e8, e=0xbfde29bc)
    at widgets/qframe.cpp:657
#19 0xb703920f in QAbstractScrollArea::viewportEvent (this=0x83e68e8, e=0x6)
    at widgets/qabstractscrollarea.cpp:947
#20 0xb70e2c28 in QAbstractItemView::viewportEvent (this=0x83e68e8, 
    event=0xbfde29bc) at itemviews/qabstractitemview.cpp:1435
#21 0xb703a5b5 in QAbstractScrollAreaFilter::eventFilter (this=0x83e9738, 
    o=0x83e8280, e=0xbfde29bc) at widgets/qabstractscrollarea_p.h:102
#22 0xb7694431 in QCoreApplicationPrivate::sendThroughObjectEventFilters (
    this=0x80b9360, receiver=0x83e8280, event=0xbfde29bc)
    at kernel/qcoreapplication.cpp:698
#23 0xb6c12f73 in QApplicationPrivate::notify_helper (this=0x80b9360, 
    receiver=0x83e8280, e=0xbfde29bc) at kernel/qapplication.cpp:3796
#24 0xb6c185bc in QApplication::notify (this=0xbfde452c, receiver=0x83e8280, 
    e=0xbfde29bc) at kernel/qapplication.cpp:3757
#25 0xb7b211c3 in KApplication::notify (this=0xbfde452c, receiver=0x83e8280, 
    event=0xbfde29bc)
    at /build/buildd/kde4libs-4.1.1+really4.1.1/kdeui/kernel/kapplication.cpp:311
#26 0xb76940b9 in QCoreApplication::notifyInternal (this=0xbfde452c, 
    receiver=0x83e8280, event=0xbfde29bc) at kernel/qcoreapplication.cpp:591
#27 0xb6c8bb5c in QX11Data::xdndHandleDrop (this=0x80bccc8, xe=0xbfde2a88, 
    passive=false)
    at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:215
#28 0xb6c8bebc in QDragManager::drop (this=0x83741f0)
    at kernel/qdnd_x11.cpp:1690
#29 0xb6c8f44d in QDragManager::eventFilter (this=0x83741f0, o=0x844bc28, 
    e=0xbfde2f4c) at kernel/qdnd_x11.cpp:1290
#30 0xb76944f8 in QCoreApplicationPrivate::sendThroughApplicationEventFilters
    (this=0x80b9360, receiver=0x844bc28, event=0xbfde2f4c)
    at kernel/qcoreapplication.cpp:680
#31 0xb6c12f13 in QApplicationPrivate::notify_helper (this=0x80b9360, 
    receiver=0x844bc28, e=0xbfde2f4c) at kernel/qapplication.cpp:3775
#32 0xb6c18125 in QApplication::notify (this=0xbfde452c, receiver=0x844bc28, 
    e=0xbfde2f4c) at kernel/qapplication.cpp:3527
#33 0xb7b211c3 in KApplication::notify (this=0xbfde452c, receiver=0x844bc28, 
    event=0xbfde2f4c)
    at /build/buildd/kde4libs-4.1.1+really4.1.1/kdeui/kernel/kapplication.cpp:311
#34 0xb76940b9 in QCoreApplication::notifyInternal (this=0xbfde452c, 
    receiver=0x844bc28, event=0xbfde2f4c) at kernel/qcoreapplication.cpp:591
#35 0xb6c15661 in QApplicationPrivate::sendMouseEvent (receiver=0x844bc28, 
    event=0xbfde2f4c, alienWidget=0x0, nativeWidget=0x844bc28, 
    buttonDown=0xb7408a10, lastMouseReceiver=@0xb7408a14)
    at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:218
#36 0xb6c7f52d in QETWidget::translateMouseEvent (this=0x844bc28, 
    event=0xbfde3468) at kernel/qapplication_x11.cpp:4048
#37 0xb6c7dee1 in QApplication::x11ProcessEvent (this=0xbfde452c, 
    event=0xbfde3468) at kernel/qapplication_x11.cpp:3166
#38 0xb6ca6c2a in x11EventSourceDispatch (s=0x80bc208, callback=0, 
    user_data=0x0) at kernel/qguieventdispatcher_glib.cpp:148
#39 0xb62e0dd6 in g_main_context_dispatch () from /usr/lib/libglib-2.0.so.0
#40 0xb62e4193 in ?? () from /usr/lib/libglib-2.0.so.0
#41 0xb62e474e in g_main_context_iteration () from /usr/lib/libglib-2.0.so.0
#42 0xb76bf9f8 in QEventDispatcherGlib::processEvents (this=0x80b9418, 
    flags=@0xbfde3608) at kernel/qeventdispatcher_glib.cpp:325
#43 0xb6ca6a25 in QGuiEventDispatcherGlib::processEvents (this=0x80b9418, 
    flags=@0xbfde3638) at kernel/qguieventdispatcher_glib.cpp:204
#44 0xb769333d in QEventLoop::processEvents (this=0x82c8280, 
    flags=@0xbfde3674) at kernel/qeventloop.cpp:149
#45 0xb76934cd in QEventLoop::exec (this=0x82c8280, flags=@0xbfde36e8)
    at kernel/qeventloop.cpp:200
#46 0xb6c8f11b in QDragManager::drag (this=0x83741f0, o=0x85eb6d0)
    at kernel/qdnd_x11.cpp:1950
#47 0xb6c2570d in QDrag::exec (this=0x85eb6d0, supportedActions=@0xbfde37b0, 
    defaultDropAction=Qt::IgnoreAction) at kernel/qdrag.cpp:281
#48 0xb6c257a4 in QDrag::exec (this=0x85eb6d0, supportedActions=@0xbfde381c)
    at kernel/qdrag.cpp:240
#49 0xb7e54412 in KUrlComboBox::mouseMoveEvent (this=0x82d1268, 
    event=0xbfde3d5c)
    at /build/buildd/kde4libs-4.1.1+really4.1.1/kio/kfile/kurlcombobox.cpp:426
#50 0xb6c6af41 in QWidget::event (this=0x82d1268, event=0xbfde3d5c)
    at kernel/qwidget.cpp:7006
#51 0xb6f731c7 in QComboBox::event (this=0x82d1268, event=0xbfde3d5c)
    at widgets/qcombobox.cpp:2616
#52 0xb6c12f9c in QApplicationPrivate::notify_helper (this=0x80b9360, 
    receiver=0x82d1268, e=0xbfde3d5c) at kernel/qapplication.cpp:3800
#53 0xb6c18125 in QApplication::notify (this=0xbfde452c, receiver=0x82d1268, 
    e=0xbfde3d5c) at kernel/qapplication.cpp:3527
#54 0xb7b211c3 in KApplication::notify (this=0xbfde452c, receiver=0x82d1268, 
    event=0xbfde3d5c)
    at /build/buildd/kde4libs-4.1.1+really4.1.1/kdeui/kernel/kapplication.cpp:311
#55 0xb76940b9 in QCoreApplication::notifyInternal (this=0xbfde452c, 
    receiver=0x82d1268, event=0xbfde3d5c) at kernel/qcoreapplication.cpp:591
#56 0xb6c15661 in QApplicationPrivate::sendMouseEvent (receiver=0x82d1268, 
    event=0xbfde3d5c, alienWidget=0x82d1268, nativeWidget=0x82c5990, 
    buttonDown=0xb7408a10, lastMouseReceiver=@0xb7408a14)
    at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:218
#57 0xb6c7f52d in QETWidget::translateMouseEvent (this=0x82c5990, 
    event=0xbfde4278) at kernel/qapplication_x11.cpp:4048
#58 0xb6c7dee1 in QApplication::x11ProcessEvent (this=0xbfde452c, 
    event=0xbfde4278) at kernel/qapplication_x11.cpp:3166
#59 0xb6ca6c2a in x11EventSourceDispatch (s=0x80bc208, callback=0, 
    user_data=0x0) at kernel/qguieventdispatcher_glib.cpp:148
#60 0xb62e0dd6 in g_main_context_dispatch () from /usr/lib/libglib-2.0.so.0
#61 0xb62e4193 in ?? () from /usr/lib/libglib-2.0.so.0
#62 0xb62e474e in g_main_context_iteration () from /usr/lib/libglib-2.0.so.0
#63 0xb76bf9f8 in QEventDispatcherGlib::processEvents (this=0x80b9418, 
    flags=@0xbfde4418) at kernel/qeventdispatcher_glib.cpp:325
#64 0xb6ca6a25 in QGuiEventDispatcherGlib::processEvents (this=0x80b9418, 
    flags=@0xbfde4448) at kernel/qguieventdispatcher_glib.cpp:204
#65 0xb769333d in QEventLoop::processEvents (this=0xbfde44c0, 
    flags=@0xbfde4484) at kernel/qeventloop.cpp:149
#66 0xb76934cd in QEventLoop::exec (this=0xbfde44c0, flags=@0xbfde44c8)
    at kernel/qeventloop.cpp:200
#67 0xb769574d in QCoreApplication::exec () at kernel/qcoreapplication.cpp:849
#68 0xb6c12897 in QApplication::exec () at kernel/qapplication.cpp:3330
#69 0x08080a59 in ?? ()
#70 0xb6786450 in __libc_start_main () from /lib/tls/i686/cmov/libc.so.6
#71 0x080619b1 in _start ()
#0  0xb7f4c410 in __kernel_vsyscall ()

*** Bug 173770 has been marked as a duplicate of this bug. ***

Is this still happening with a current KDE version?

I can't reproduce here using:

Qt: 4.5.1 (qt-copy  958974)
KDE: 4.2.87 (KDE 4.2.87 (KDE 4.3 >= 20090519))
kdelibs svn rev. 971894 / kdebase svn rev. 971894
on ArchLinux i686 - Kernel 2.6.29.3

BTW: I could not try D&D as smb:/ doesn't list my shares..

I wonder if this could be related to bug 157283 (crash which should be fixed now)

It doesn't crash, but it won't create a new place either. Dario, the drag and drop was just selecting the network icon next (left) to the link and try to drag it to the places panel.

Dragging a normal folder to the places panel works, but not with samba ones (dragging a listed remotely shared folder). To add a samba folder to the panel it's necessary to right click it and tell it to "add to places", could be a little more friendlier.

Seems what i just said is pretty similar to that bug, still the bug stands, if it's a duplicate or not is for Peter to decide I guess.

Just to keep this place clean I suggest to close/merge this report, as the crash is no longer happening, and to open a new bug report about the smb share not being added.
Regards

@RuiG:

If you start Dolphin from konsole, are any warnings logged when you attempt the drag? In particular, "URL not added to Places as mimetype could not be determined!"?

Simon, no warnings here. I tried running dolphin from konsole but there aren't any debug messages, maybe I need debug packages. 

Anyway, I just figured that dragging the following link: smb://192.168.0.1/ doesn't create the share in the panel, but if i'm at a specific folder, such as smb://192.168.0.1/Downloads , dragging it (like described above, dragging the little network icon to the left of the link) will create a folder in the places panel with the name Downloads.

In my opinion this constitutes a different bug, "dragging a samba shared folder at root folder, places panel doesn't create it" or something. Maybe because the folder itself doesn't have a name, the panel doesn't know how to call it, and so it doesn't, but don't quote me on that (much).

I've just checked myself using smb://localhost as the URL (I have a samba share on my laptop with a couple of folders, so this is valid), and attempting to drag this to the Places sidebar does indeed output the warning I described earlier, preceeded by 

kio_smb(22104) SMBSlave::get: SMBSlave::get on  KUrl("smb://localhost/")
kio_smb(22104) SMBSlave::checkURL: checkURL  KUrl("smb://localhost/")
kio_smb(22104) SMBSlave::checkURL: checkURL return3  KUrl("smb://localhost/")
kio_smb(22104) SMBSlave::auth_initialize_smbc: auth_initialize_smbc
kio_smb(22104) SMBUrl::updateCache: updateCache  "/"
kio_smb(22104) SMBSlave::auth_smbc_get_data: AAAAAAAAAAAAAA auth_smbc_get_dat: set user= simon , workgroup= WORKGROUP  server= localhost , share=
kio_smb(22104) SMBSlave::auth_smbc_get_data: libsmb-auth-callback URL: KUrl("smb://localhost/")
kio_smb(22104)/kio (kioslave) KIO::KPasswdServer::checkAuthInfo: window-id= 0 url= KUrl("smb://localhost/")
kded(22056)/kio (KPasswdServer) KPasswdServer::checkAuthInfoAsync: User = "simon" , WindowId = 0
kio_smb(22104)/kio (kioslave) KIO::KPasswdServer::checkAuthInfo: username= "simon" password=[hidden]
kio_smb(22104) SMBSlave::cache_stat: size  0
dolphin(22041)/kio (KIOJob) KIO::SlaveInterface::dispatch: error  111   "smb://localhost/"
dolphin(22041) KFilePlacesModel::dropMimeData: URL not added to Places as mimetype could not be determined!

so it looks like it has roughly the same root cause as https://bugs.kde.org/show_bug.cgi?id=165485

Sorry for Spam, but I've just tried Rui's suggestion of using a non-root smb:/ URL (smb://localhost/apt-archives) and now get:

kio_smb(22559) SMBSlave::get: SMBSlave::get on  KUrl("smb://localhost/apt-archives")
kio_smb(22559) SMBSlave::checkURL: checkURL  KUrl("smb://localhost/apt-archives")
kio_smb(22559) SMBSlave::checkURL: checkURL return3  KUrl("smb://localhost/apt-archives")
kio_smb(22559) SMBSlave::auth_initialize_smbc: auth_initialize_smbc
kio_smb(22559) SMBUrl::updateCache: updateCache  "/apt-archives"
kio_smb(22559) SMBSlave::auth_smbc_get_data: AAAAAAAAAAAAAA auth_smbc_get_dat: set user= simon , workgroup= WORKGROUP  server= localhost , share= apt-archives
kio_smb(22559) SMBSlave::auth_smbc_get_data: libsmb-auth-callback URL: KUrl("smb://localhost/apt-archives")
kio_smb(22559)/kio (kioslave) KIO::KPasswdServer::checkAuthInfo: window-id= 0 url= KUrl("smb://localhost/apt-archives")
kded(22056)/kio (KPasswdServer) KPasswdServer::checkAuthInfoAsync: User = "simon" , WindowId = 0
kio_smb(22559)/kio (kioslave) KIO::KPasswdServer::checkAuthInfo: username= "simon" password=[hidden]
kio_smb(22559) SMBSlave::cache_stat: size  0
dolphin(22041)/kio (KIOJob) KIO::SlaveInterface::dispatch: error  109   "smb://localhost/apt-archives"
dolphin(22041)/kio (KIOJob) KIO::MimetypeJob::slotFinished: It is in fact a directory!

Still a dispatch error (with a different code), but this time it is able to tell the mimetype (a directory) so as you note, the problem is that smb:// roots aren't being correctly identified as directories.  I've CC'd dfaure as he fixed #165485 and so that you have two Akademy Award winners on the case ;)

Please also see bug ID 202439, "Dolphin crashes when adding SFTP location to places"

This is fixed now as bug 173297 / bug 157283.
@Simon: if you are still seeing that errors in the output, you should create a new bug report against kio/smb. Do not forget to add your KDE4 version and your GNU/Linux distribution. 
Thanks