Another possible backtrace of this, reproduced with the same steps.
Application: KGet (kget), signal: Segmentation fault
[Current thread is 1 (Thread 0x7fa88c107760 (LWP 20862))]

Thread 2 (Thread 0x7fa878144710 (LWP 20867)):
#0  pthread_cond_timedwait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_timedwait.S:211
#1  0x00007fa88925bdf2 in QWaitConditionPrivate::wait (this=<value optimized out>, mutex=0xfb7eb0, time=30000) at thread/qwaitcondition_unix.cpp:85
#2  QWaitCondition::wait (this=<value optimized out>, mutex=0xfb7eb0, time=30000) at thread/qwaitcondition_unix.cpp:159
#3  0x00007fa889250e21 in QThreadPoolThread::run (this=0x11affd0) at concurrent/qthreadpool.cpp:140
#4  0x00007fa88925ae35 in QThreadPrivate::start (arg=0x11affd0) at thread/qthread_unix.cpp:248
#5  0x00007fa88a2ff8ba in start_thread (arg=<value optimized out>) at pthread_create.c:300
#6  0x00007fa887ab401d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:112
#7  0x0000000000000000 in ?? ()

Thread 1 (Thread 0x7fa88c107760 (LWP 20862)):
[KCrash Handler]
#5  QUrlPrivate::parse (this=0xee7a20, parseOptions=QUrlPrivate::ParseAndSet) at io/qurl.cpp:3742
#6  0x00007fa889306efa in QUrl::operator== (this=0x7fffcb6ddab0, url=...) at io/qurl.cpp:5903
#7  0x00007fa88b5500e0 in KDirModel::expandToUrl (this=0xee78d0, url=<value optimized out>) at ../../kio/kio/kdirmodel.cpp:1085
#8  0x00007fa878185bfa in KDirOperator::setCurrentItem (this=0xee79f0, url=...) at ../../kfile/kdiroperator.cpp:1737
#9  0x00007fa87819bb09 in KFileWidgetPrivate::_k_slotLoadingFinished (this=0xede900) at ../../kfile/kfilewidget.cpp:1511
#10 0x00007fa8781a7654 in KFileWidget::qt_metacall (this=0xbf8fb0, _c=QMetaObject::InvokeMetaMethod, _id=<value optimized out>, _a=0x7fffcb6ddd40) at ./kfilewidget.moc:146
#11 0x00007fa88935d346 in QMetaObject::activate (sender=0xee79f0, m=<value optimized out>, local_signal_index=<value optimized out>, argv=0x97d00) at kernel/qobject.cpp:3295
#12 0x00007fa8781813cc in KDirOperator::Private::_k_slotCanceled (this=0xeb5560) at ../../kfile/kdiroperator.cpp:2289
#13 0x00007fa87818c395 in KDirOperator::qt_metacall (this=0xee79f0, _c=QMetaObject::InvokeMetaMethod, _id=<value optimized out>, _a=0x7fffcb6dde70) at ./kdiroperator.moc:247
#14 0x00007fa88935d346 in QMetaObject::activate (sender=0xf33040, m=<value optimized out>, local_signal_index=<value optimized out>, argv=0x97d00) at kernel/qobject.cpp:3295
#15 0x00007fa88b5353b8 in KDirListerCache::stop (this=0xe8e8b0, lister=0xf33040, silent=false) at ../../kio/kio/kdirlister.cpp:378
#16 0x00007fa88b53f155 in ~KDirLister (this=0xee7a20, __in_chrg=<value optimized out>) at ../../kio/kio/kdirlister.cpp:1938
#17 0x00007fa889358b9c in QObjectPrivate::deleteChildren (this=0xe9f3b0) at kernel/qobject.cpp:1986
#18 0x00007fa88935fc7f in ~QObject (this=<value optimized out>, __in_chrg=<value optimized out>) at kernel/qobject.cpp:975
#19 0x00007fa88933d435 in ~QAbstractItemModel (this=0xee78d0, __in_chrg=<value optimized out>) at kernel/qabstractitemmodel.cpp:1373
#20 0x00007fa88b54dc0a in ~KDirModel (this=0xee78d0, __in_chrg=<value optimized out>) at ../../kio/kio/kdirmodel.cpp:331
#21 0x00007fa878183bcc in ~Private (this=0xeb5560, __in_chrg=<value optimized out>) at ../../kfile/kdiroperator.cpp:351
#22 0x00007fa878183d6f in ~KDirOperator (this=0xee79f0, __in_chrg=<value optimized out>) at ../../kfile/kdiroperator.cpp:423
#23 0x00007fa87819d02f in ~KFileWidgetPrivate (this=0xbf8fb0, __in_chrg=<value optimized out>) at ../../kfile/kfilewidget.cpp:107
#24 ~KFileWidget (this=0xbf8fb0, __in_chrg=<value optimized out>) at ../../kfile/kfilewidget.cpp:643
#25 0x00007fa889358b9c in QObjectPrivate::deleteChildren (this=0xe42f80) at kernel/qobject.cpp:1986
#26 0x00007fa8887472fd in ~QWidget (this=0xc327a0, __in_chrg=<value optimized out>) at kernel/qwidget.cpp:1476
#27 0x00007fa88b618ea5 in ~KFileDialog (this=0xc327a0, __in_chrg=<value optimized out>) at ../../kio/kfile/kfiledialog.cpp:326
#28 0x00007fa88af440f3 in KGet::destFileInputDialog (destDir=<value optimized out>, suggestedFileName=...) at ../../kget/core/kget.cpp:883
#29 0x00007fa88af4995d in KGet::addTransfer (srcUrl=) at ../../kget/core/kget.cpp:228
#30 0x00000000004abfe4 in KGetApp::newInstance() ()
#31 0x00007fa88bb23256 in KUniqueApplicationAdaptor::newInstance (this=0xac1590, asn_id=<value optimized out>, args=...) at ../../kdeui/kernel/kuniqueapplication.cpp:454
#32 0x00007fa88bb23896 in KUniqueApplicationAdaptor::qt_metacall (this=0xac1590, _c=QMetaObject::InvokeMetaMethod, _id=15628832, _a=0x7fffcb6deae0) at ./kuniqueapplication_p.moc:81
#33 0x00007fa889688421 in QDBusConnectionPrivate::deliverCall (this=<value optimized out>, object=<value optimized out>, msg=<value optimized out>, metaTypes=..., slotIdx=<value optimized out>)
    at qdbusintegrator.cpp:904
#34 0x00007fa88968968b in QDBusConnectionPrivate::activateCall (this=<value optimized out>, object=0xac1590, flags=337, msg=...) at qdbusintegrator.cpp:816
#35 0x00007fa88968a10d in QDBusConnectionPrivate::activateObject (this=<value optimized out>, node=<value optimized out>, msg=..., pathStartPos=<value optimized out>) at qdbusintegrator.cpp:1364
#36 0x00007fa88968a3a8 in QDBusActivateObjectEvent::placeMetaCall (this=0x10a5d30) at qdbusintegrator.cpp:1477
#37 0x00007fa889359e89 in QObject::event (this=0x7fffcb6dfab0, e=0x10a5d30) at kernel/qobject.cpp:1248
#38 0x00007fa8886ee69d in QApplication::event (this=0x7fffcb6dfab0, e=0x10a5d30) at kernel/qapplication.cpp:2355
#39 0x00007fa8886ea32c in QApplicationPrivate::notify_helper (this=0x9f2760, receiver=0x7fffcb6dfab0, e=0x10a5d30) at kernel/qapplication.cpp:4302
#40 0x00007fa8886f080b in QApplication::notify (this=0x7fffcb6dfab0, receiver=0x7fffcb6dfab0, e=0x10a5d30) at kernel/qapplication.cpp:4185
#41 0x00007fa88bb1c436 in KApplication::notify (this=0x7fffcb6dfab0, receiver=0x7fffcb6dfab0, event=0x10a5d30) at ../../kdeui/kernel/kapplication.cpp:302
#42 0x00007fa88934a15c in QCoreApplication::notifyInternal (this=0x7fffcb6dfab0, receiver=0x7fffcb6dfab0, event=0x10a5d30) at kernel/qcoreapplication.cpp:726
#43 0x00007fa88934d804 in QCoreApplication::sendEvent (receiver=0x0, event_type=<value optimized out>, data=0x9a16f0) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:215
#44 QCoreApplicationPrivate::sendPostedEvents (receiver=0x0, event_type=<value optimized out>, data=0x9a16f0) at kernel/qcoreapplication.cpp:1367
#45 0x00007fa889373bd3 in QCoreApplication::sendPostedEvents (s=<value optimized out>) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:220
#46 postEventSourceDispatch (s=<value optimized out>) at kernel/qeventdispatcher_glib.cpp:276
#47 0x00007fa8837686c2 in g_main_context_dispatch () from /lib/libglib-2.0.so.0
#48 0x00007fa88376c538 in ?? () from /lib/libglib-2.0.so.0
#49 0x00007fa88376c6ec in g_main_context_iteration () from /lib/libglib-2.0.so.0
#50 0x00007fa889373713 in QEventDispatcherGlib::processEvents (this=0x9a1200, flags=<value optimized out>) at kernel/qeventdispatcher_glib.cpp:412
#51 0x00007fa88879a14e in QGuiEventDispatcherGlib::processEvents (this=0xee7a20, flags=<value optimized out>) at kernel/qguieventdispatcher_glib.cpp:204
#52 0x00007fa889348a82 in QEventLoop::processEvents (this=<value optimized out>, flags=) at kernel/qeventloop.cpp:149
#53 0x00007fa889348e5c in QEventLoop::exec (this=0x7fffcb6dfa10, flags=) at kernel/qeventloop.cpp:201
#54 0x00007fa88934daeb in QCoreApplication::exec () at kernel/qcoreapplication.cpp:1003
#55 0x00000000004aa50d in main (argc=<value optimized out>, argv=<value optimized out>) at ../../kget/main.cpp:184

I am afraid we can't fix this for 4.4 since there won't be a new release of that, though we hope to fix this for 4.5. Sorry for the inconvenience this bug caused.

####
Dev-info

This is the code where it crashes:

kget.cpp:
KUrl KGet::destFileInputDialog(QString destDir, const QString& suggestedFileName) // krazy:exclude=passbyvalue
{
    if (destDir.isEmpty())
        destDir = generalDestDir();

    // open the filedialog for confirmation
    QPointer<KFileDialog> dlg = new KFileDialog(destDir, QString(), 0, 0);
    dlg->setCaption(i18n("Save As"));
    dlg->setOperationMode(KFileDialog::Saving);
    dlg->setMode(KFile::File | KFile::LocalOnly);

    // Use the destination name if not empty...
    if (!suggestedFileName.isEmpty())
        dlg->setSelection(suggestedFileName);

    KUrl destUrl;
    if (dlg->exec() != QDialog::Rejected){
        destUrl = dlg->selectedUrl();
        Settings::setLastDirectory(destUrl.directory(KUrl::ObeyTrailingSlash));
    }

    delete dlg;
    return destUrl;
}

Line 883 is the one with "delete dlg;".
So maybe the way we use KFileDialog is compeletly wrong (?) and we will use one of the static method as (hopefully) workaround, though I still think that this is a bug.

SVN commit 1144613 by mfuchs:

Uses a static method to get the download-destination.
CCBUG:243093

 M  +6 -12     kget.cpp  


WebSVN link: http://websvn.kde.org/?view=rev&revision=1144613

SVN commit 1144614 by mfuchs:

Fowardport r1144613
Uses a static method to get the download-destination.
CCBUG:243093

 M  +6 -12     kget.cpp  


WebSVN link: http://websvn.kde.org/?view=rev&revision=1144614

SVN commit 1144617 by dfaure:

Ensure that slotCanceled (called via KDirLister's stop()) doesn't trigger more stuff while we're already in the destructor.
FIXED-IN: 4.5
  (I'll backport)
BUG: 243093


 M  +1 -0      kdiroperator.cpp  


WebSVN link: http://websvn.kde.org/?view=rev&revision=1144617

SVN commit 1144620 by dfaure:

Backport: Ensure that slotCanceled (called via KDirLister's stop()) doesn't trigger more stuff while we're already in the destructor.
CCBUG: 243093


 M  +1 -0      kdiroperator.cpp  


WebSVN link: http://websvn.kde.org/?view=rev&revision=1144620

*** Bug 242085 has been marked as a duplicate of this bug. ***

*** Bug 204318 has been marked as a duplicate of this bug. ***

*** Bug 210446 has been marked as a duplicate of this bug. ***

*** Bug 215179 has been marked as a duplicate of this bug. ***