the backtrace isn't really complete try to reproduce after installing all the debug symbols with the instructions of 
http://techbase.kde.org/Development/Tutorials/Debugging/How_to_create_useful_crash_reports

Looks like a crash related to system tray plasmoid. That plasmoid was reworked a lot for KDE4.2. Have anyone experienced this bug with a devel version of KDE ? (4.2(beta1/beta2/svn)) ?

I get this whenever I boot up. I have tried to load plasma but I just get this error. I am able to run programs still thru alt+f2. However my desktop is completely blank. The only thing I may have done was run an update thru Adept earlier that day. When I booted up later and this is what I got.

Application: Plasma Workspace (plasma), signal SIGSEGV
(no debugging symbols found)
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[Thread debugging using libthread_db enabled]
[New Thread 0xb48246e0 (LWP 23242)]
[New Thread 0xb2b87b90 (LWP 23243)]
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
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[KCrash handler]
#6  0xb7251527 in QGraphicsLinearLayout::insertItem ()
   from /usr/lib/libQtGui.so.4
#7  0xb2cbaaeb in ?? () from /usr/lib/kde4/plasma_applet_devicenotifier.so
#8  0xb7dfb585 in Plasma::Applet::flushPendingConstraintsEvents ()
   from /usr/lib/libplasma.so.2
#9  0xb7dfbbc6 in Plasma::Applet::timerEvent () from /usr/lib/libplasma.so.2
#10 0xb771b53f in QObject::event () from /usr/lib/libQtCore.so.4
#11 0xb7254447 in QGraphicsWidget::event () from /usr/lib/libQtGui.so.4
#12 0xb6c948ec in QApplicationPrivate::notify_helper ()
   from /usr/lib/libQtGui.so.4
#13 0xb6c9c72e in QApplication::notify () from /usr/lib/libQtGui.so.4
#14 0xb7bdab2d in KApplication::notify () from /usr/lib/libkdeui.so.5
#15 0xb770be61 in QCoreApplication::notifyInternal ()
   from /usr/lib/libQtCore.so.4
#16 0xb7739d81 in ?? () from /usr/lib/libQtCore.so.4
#17 0xb7736520 in ?? () from /usr/lib/libQtCore.so.4
#18 0xb5a176f8 in g_main_context_dispatch () from /usr/lib/libglib-2.0.so.0
#19 0xb5a1ada3 in ?? () from /usr/lib/libglib-2.0.so.0
#20 0xb5a1af61 in g_main_context_iteration () from /usr/lib/libglib-2.0.so.0
#21 0xb7736478 in QEventDispatcherGlib::processEvents ()
   from /usr/lib/libQtCore.so.4
#22 0xb6d2eea5 in ?? () from /usr/lib/libQtGui.so.4
#23 0xb770a52a in QEventLoop::processEvents () from /usr/lib/libQtCore.so.4
#24 0xb770a6ea in QEventLoop::exec () from /usr/lib/libQtCore.so.4
#25 0xb69493eb in KIO::NetAccess::enter_loop () from /usr/lib/libkio.so.5
#26 0xb69495ec in KIO::NetAccess::statInternal () from /usr/lib/libkio.so.5
#27 0xb694a3fb in KIO::NetAccess::stat () from /usr/lib/libkio.so.5
#28 0xb694a47b in KIO::NetAccess::mostLocalUrl () from /usr/lib/libkio.so.5
#29 0xb2bbff1e in ?? () from /usr/lib/kde4/plasma_applet_icon.so
#30 0xb2bc06ff in ?? () from /usr/lib/kde4/plasma_applet_icon.so
#31 0xb7e2b737 in Plasma::Corona::loadLayout () from /usr/lib/libplasma.so.2
#32 0xb7e2c531 in Plasma::Corona::initializeLayout ()
   from /usr/lib/libplasma.so.2
#33 0xb8091199 in ?? () from /usr/lib/libkdeinit4_plasma.so
#34 0xb8092880 in ?? () from /usr/lib/libkdeinit4_plasma.so
#35 0xb8094a81 in ?? () from /usr/lib/libkdeinit4_plasma.so
#36 0xb808643a in kdemain () from /usr/lib/libkdeinit4_plasma.so
#37 0x080485b2 in _start ()
#0  0xb80d0430 in __kernel_vsyscall ()


Thanks

Eric: your bug is not the same this one. in future, unless the backtraces are *identical* (which in this case they obviously are not), please open a NEW report with your backtrace in it.

also consider installing the debug packages so you can produce full backtraces as well:

http://techbase.kde.org/Development/Tutorials/Debugging/How_to_create_useful_crash_reports

in any case, your bug is fixed in svn.

kubuntu 8.10 - happened after ktwitter widget sign-in...

Application: Plasma Workspace (plasma), signal SIGSEGV
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
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(no debugging symbols found)
(no debugging symbols found)
[Thread debugging using libthread_db enabled]
[New Thread 0xb544a6c0 (LWP 5383)]
[New Thread 0xb2e33b90 (LWP 5389)]
[New Thread 0xb379ab90 (LWP 5388)]
(no debugging symbols found)
(no debugging symbols found)
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[KCrash handler]
#6  0xb70900dd in QGraphicsItem::clearFocus () from /usr/lib/libQtGui.so.4
#7  0xb70d9184 in ?? () from /usr/lib/libQtGui.so.4
#8  0xb70d7f06 in QGraphicsWidget::itemChange () from /usr/lib/libQtGui.so.4
#9  0xb7c79c1d in Plasma::Applet::itemChange () from /usr/lib/libplasma.so.2
#10 0xb709a525 in QGraphicsItem::setParentItem () from /usr/lib/libQtGui.so.4
#11 0xb7c993fc in ?? () from /usr/lib/libplasma.so.2
#12 0xb7ca2d25 in Plasma::Containment::sceneEventFilter ()
   from /usr/lib/libplasma.so.2
#13 0xb70b1457 in ?? () from /usr/lib/libQtGui.so.4
#14 0xb70b1513 in ?? () from /usr/lib/libQtGui.so.4
#15 0xb70b2a2a in ?? () from /usr/lib/libQtGui.so.4
#16 0xb70ba1e3 in ?? () from /usr/lib/libQtGui.so.4
#17 0xb70ba5af in QGraphicsScene::mouseMoveEvent ()
   from /usr/lib/libQtGui.so.4
#18 0xb70ba7c7 in QGraphicsScene::event () from /usr/lib/libQtGui.so.4
#19 0xb6b168ec in QApplicationPrivate::notify_helper ()
   from /usr/lib/libQtGui.so.4
#20 0xb6b1e72e in QApplication::notify () from /usr/lib/libQtGui.so.4
#21 0xb7a5cb2d in KApplication::notify () from /usr/lib/libkdeui.so.5
#22 0xb758de61 in QCoreApplication::notifyInternal ()
   from /usr/lib/libQtCore.so.4
#23 0xb70c7d88 in ?? () from /usr/lib/libQtGui.so.4
#24 0xb70d0316 in QGraphicsView::mouseMoveEvent () from /usr/lib/libQtGui.so.4
#25 0xb6b6e7cb in QWidget::event () from /usr/lib/libQtGui.so.4
#26 0xb6ea5fd3 in QFrame::event () from /usr/lib/libQtGui.so.4
#27 0xb6f3c7df in QAbstractScrollArea::viewportEvent ()
   from /usr/lib/libQtGui.so.4
#28 0xb70c9d0f in QGraphicsView::viewportEvent () from /usr/lib/libQtGui.so.4
#29 0xb6f3ed85 in ?? () from /usr/lib/libQtGui.so.4
#30 0xb758d04a in QCoreApplicationPrivate::sendThroughObjectEventFilters ()
   from /usr/lib/libQtCore.so.4
#31 0xb6b168ca in QApplicationPrivate::notify_helper ()
   from /usr/lib/libQtGui.so.4
#32 0xb6b1f0e1 in QApplication::notify () from /usr/lib/libQtGui.so.4
#33 0xb7a5cb2d in KApplication::notify () from /usr/lib/libkdeui.so.5
#34 0xb758de61 in QCoreApplication::notifyInternal ()
   from /usr/lib/libQtCore.so.4
#35 0xb6b1e36e in QApplicationPrivate::sendMouseEvent ()
   from /usr/lib/libQtGui.so.4
#36 0xb6b88656 in ?? () from /usr/lib/libQtGui.so.4
#37 0xb6b879e5 in QApplication::x11ProcessEvent () from /usr/lib/libQtGui.so.4
#38 0xb6bb17aa in ?? () from /usr/lib/libQtGui.so.4
#39 0xb58db6f8 in g_main_context_dispatch () from /usr/lib/libglib-2.0.so.0
#40 0xb58deda3 in ?? () from /usr/lib/libglib-2.0.so.0
#41 0xb58def61 in g_main_context_iteration () from /usr/lib/libglib-2.0.so.0
#42 0xb75b8478 in QEventDispatcherGlib::processEvents ()
   from /usr/lib/libQtCore.so.4
#43 0xb6bb0ea5 in ?? () from /usr/lib/libQtGui.so.4
#44 0xb758c52a in QEventLoop::processEvents () from /usr/lib/libQtCore.so.4
#45 0xb758c6ea in QEventLoop::exec () from /usr/lib/libQtCore.so.4
#46 0xb758eda5 in QCoreApplication::exec () from /usr/lib/libQtCore.so.4
#47 0xb6b16767 in QApplication::exec () from /usr/lib/libQtGui.so.4
#48 0xb7f08491 in kdemain () from /usr/lib/libkdeinit4_plasma.so
#49 0x080485b2 in _start ()
#0  0xb7f4f430 in __kernel_vsyscall ()

James, your crash is something else. Please confirm than when you sign in Twitter with the small Settings icon on the applet handle instead of the Configure button and you see no crash.
Thanks in advance!

I have the same problem, I see this error message on every login. I have KDE 4.2.0 (released 27.1.2009) and ArchLinux.

Unfortunately the backtrace isn't very useful.

(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
[Thread debugging using libthread_db enabled]
[New Thread 0xb48b49e0 (LWP 26037)]
[New Thread 0xa87b6b90 (LWP 26039)]
[New Thread 0xa90b1b90 (LWP 26038)]
0xb802f424 in __kernel_vsyscall ()
[Current thread is 0 (LWP 26037)]

Thread 3 (Thread 0xa90b1b90 (LWP 26038)):
#0  0xb802f424 in __kernel_vsyscall ()
#1  0xb6926c55 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib/libpthread.so.0
#2  0xb69b56a2 in QWaitCondition::wait () from /usr/lib/libQtCore.so.4
#3  0xb7aaba0a in ?? () from /usr/lib/libQtNetwork.so.4
#4  0x096ba668 in ?? ()
#5  0x096ba664 in ?? ()
#6  0xffffffff in ?? ()
#7  0xb730ad50 in ?? ()
#8  0xa90b12f0 in ?? ()
#9  0xb803e41b in _dl_fixup () from /lib/ld-linux.so.2
#10 0xb69b4910 in ?? () from /usr/lib/libQtCore.so.4
#11 0x096ba658 in ?? ()
#12 0x00000000 in ?? ()

Thread 2 (Thread 0xa87b6b90 (LWP 26039)):
#0  0xb802f424 in __kernel_vsyscall ()
#1  0xb6926c55 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib/libpthread.so.0
#2  0xb69b56a2 in QWaitCondition::wait () from /usr/lib/libQtCore.so.4
#3  0xa977080a in RenderThread::run () from /usr/lib/kde4/plasma_wallpaper_image.so
#4  0xb69b4910 in ?? () from /usr/lib/libQtCore.so.4
#5  0x090ac334 in ?? ()
#6  0x00000000 in ?? ()

Thread 1 (Thread 0xb48b49e0 (LWP 26037)):
#0  0xb802f424 in __kernel_vsyscall ()
#1  0xb674b5d6 in nanosleep () from /lib/libc.so.6
#2  0xb674b3be in sleep () from /lib/libc.so.6
#3  0xb78ccde8 in KCrash::startDrKonqi () from /usr/lib/libkdeui.so.5
#4  0xb78cd7b4 in KCrash::defaultCrashHandler () from /usr/lib/libkdeui.so.5
#5  <signal handler called>
#6  0xb67270e6 in memcpy () from /lib/libc.so.6
#7  0x00000000 in ?? ()
#0  0xb802f424 in __kernel_vsyscall ()

@Jakub: your crash seems to be a different one.
BTW: you need debug symbols to get useful information in the backtrace. Please recompile kdelibs and kdebase-workspace PKGBUILD using the "!strip" option and change the"-DCMAKE_BUILD_TYPE" option (cmake) from "Release" to "debugfull" in the build function

Renaming the report to avoid confusions

Any news on the original report? It should be fixed now on KDE4.2/4.3+

As far as I am concerned, this report can be closed. After I upgraded to KDE 4.2.1 the issue has not recurred. Using Mandriva 2009,0 with the unofficial media sources on the KDE.org ftp mirror at ftp://ftp.kde.org/pub/kde/stable/4.2.1/Mandriva/2009.0/RPMS/x86_64 and all is well. Excellent piece of work. THank You all!

I'm glad it works now. Marking as WORKSFORME