Application: kmix (3.6-alpha2)
KDE Platform Version: 4.4.1 (KDE 4.4.1) (Compiled from sources)
Qt Version: 4.6.2
Operating System: Linux 2.6.31-gentoo-r10 x86_64
Distribution (Platform): Gentoo Packages

-- Information about the crash:
First off, regarding platform: Reproducible on Kubuntu karmic, Gentoo and Arch (x64 all).
There are several threads in the Kubuntu forums regarding plasma crashes on upgrade to 4.4 and I suspect a lot of them involved themes. 

Plasma (and on Kubuntu and Arch, kwin) crashes any time I try to customize a widget theme. For an example, lets take BlackGlass from kde-look.org (http://kde-look.org/content/show.php/BlackGlass?content=110034). Note that this can be reproduced by most themes, including the most popular Glassified. Let's start with one of the standard pre-installed themes, say slim glow. Now go to SystemSettings -> Appearance -> Workspace and select the newly install BlackGlass. Wait a few secs for the crash. On gentoo, my desktop recovers by itself. On Kubuntu and Arch, I have to do Alt+F2 -> plasma-workspace (and sometimes kwin --replace). 

It took me absolutely ages to figure out how to get the debugging symbols installed to be able to report this crash and I do hope this is useful. BTW, I can get plasma to crash by customizing any of the above themes in 4.3.5. For example, change  Advanced -> Desktop Theme Details -> Panel Background to use BlackGlass Background or Glassified results in a similar Plasma and/or Kwin crash.

The crash can be reproduced every time.

 -- Backtrace:
Application: KMix (kdeinit4), signal: Bus error
[KCrash Handler]
#5  0x00007f7f7307d6f7 in KPixmapCache::Private::mmapFile (this=0xf92f60, filename=..., info=0xf92fc8, newsize=126341120)
    at /var/tmp/portage/kde-base/kdelibs-4.4.1-r1/work/kdelibs-4.4.1/kdeui/util/kpixmapcache.cpp:491
#6  0x00007f7f7307e85c in KPixmapCache::Private::mmapFiles (this=0xf92f60) at /var/tmp/portage/kde-base/kdelibs-4.4.1-r1/work/kdelibs-4.4.1/kdeui/util/kpixmapcache.cpp:424
#7  0x00007f7f7307df5c in KPixmapCache::recreateCacheFiles (this=0x10675b0) at /var/tmp/portage/kde-base/kdelibs-4.4.1-r1/work/kdelibs-4.4.1/kdeui/util/kpixmapcache.cpp:1247
#8  0x00007f7f7307e227 in KPixmapCache::Private::checkFileVersion (this=0xf92f60, filename=...) at /var/tmp/portage/kde-base/kdelibs-4.4.1-r1/work/kdelibs-4.4.1/kdeui/util/kpixmapcache.cpp:741
#9  0x00007f7f7307e63c in KPixmapCache::Private::init (this=0xf92f60) at /var/tmp/portage/kde-base/kdelibs-4.4.1-r1/work/kdelibs-4.4.1/kdeui/util/kpixmapcache.cpp:1052
#10 0x00007f7f7307f8b3 in KPixmapCache::discard (this=0x10675b0) at /var/tmp/portage/kde-base/kdelibs-4.4.1-r1/work/kdelibs-4.4.1/kdeui/util/kpixmapcache.cpp:1279
#11 0x00007f7f7307fe6e in KPixmapCache::deleteCache (name=...) at /var/tmp/portage/kde-base/kdelibs-4.4.1-r1/work/kdelibs-4.4.1/kdeui/util/kpixmapcache.cpp:1255
#12 0x00007f7f6bec0fbe in Plasma::ThemePrivate::discardCache (this=0xf8dbd0) at /var/tmp/portage/kde-base/kdelibs-4.4.1-r1/work/kdelibs-4.4.1/plasma/theme.cpp:221
#13 0x00007f7f6bec11f1 in Plasma::ThemePrivate::compositingChanged (this=0xf8dbd0) at /var/tmp/portage/kde-base/kdelibs-4.4.1-r1/work/kdelibs-4.4.1/plasma/theme.cpp:213
#14 0x00007f7f6bec25e4 in Plasma::Theme::qt_metacall (this=0xf8db10, _c=QMetaObject::InvokeMetaMethod, _id=<value optimized out>, _a=0x7fffa242ca40)
    at /var/tmp/portage/kde-base/kdelibs-4.4.1-r1/work/kdelibs-4.4.1_build/plasma/theme.moc:108
#15 0x00007f7f728a99f0 in QMetaObject::activate(QObject*, QMetaObject const*, int, void**) () from /usr/lib64/qt4/libQtCore.so.4
#16 0x00007f7f730788a3 in KSelectionWatcher::Private::x11Event (this=<value optimized out>, ev_P=0x0)
    at /var/tmp/portage/kde-base/kdelibs-4.4.1-r1/work/kdelibs-4.4.1/kdeui/util/kmanagerselection.cpp:395
#17 0x00007f7f73016641 in KApplication::x11EventFilter (this=<value optimized out>, _event=0x7fffa242d190)
    at /var/tmp/portage/kde-base/kdelibs-4.4.1-r1/work/kdelibs-4.4.1/kdeui/kernel/kapplication.cpp:953
#18 0x00007f7f718e676e in ?? () from /usr/lib64/qt4/libQtGui.so.4
#19 0x00007f7f718f6b1d in QApplication::x11ProcessEvent(_XEvent*) () from /usr/lib64/qt4/libQtGui.so.4
#20 0x00007f7f7191d78a in ?? () from /usr/lib64/qt4/libQtGui.so.4
#21 0x00007f7f6dd02073 in g_main_context_dispatch () from /usr/lib/libglib-2.0.so.0
#22 0x00007f7f6dd0516c in ?? () from /usr/lib/libglib-2.0.so.0
#23 0x00007f7f6dd052ee in g_main_context_iteration () from /usr/lib/libglib-2.0.so.0
#24 0x00007f7f728bdc74 in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib64/qt4/libQtCore.so.4
#25 0x00007f7f7191d3a6 in ?? () from /usr/lib64/qt4/libQtGui.so.4
#26 0x00007f7f72896fb4 in QEventLoop::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib64/qt4/libQtCore.so.4
#27 0x00007f7f728972ff in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib64/qt4/libQtCore.so.4
#28 0x00007f7f728992de in QCoreApplication::exec() () from /usr/lib64/qt4/libQtCore.so.4
#29 0x00007f7f680cc536 in kdemain () from /usr/lib64/libkdeinit4_kmix.so
#30 0x000000000040726a in launch (argc=1, _name=0xe9d7e8 "/usr/bin/kmix", args=0xe9d7f6 "", cwd=0x0, envc=0, envs=<value optimized out>, reset_env=false, tty=0x0, avoid_loops=false, startup_id_str=
    0x40a9ac "0") at /var/tmp/portage/kde-base/kdelibs-4.4.1-r1/work/kdelibs-4.4.1/kinit/kinit.cpp:710
#31 0x0000000000407d0e in handle_launcher_request (sock=8, who=<value optimized out>) at /var/tmp/portage/kde-base/kdelibs-4.4.1-r1/work/kdelibs-4.4.1/kinit/kinit.cpp:1202
#32 0x000000000040830a in handle_requests (waitForPid=0) at /var/tmp/portage/kde-base/kdelibs-4.4.1-r1/work/kdelibs-4.4.1/kinit/kinit.cpp:1395
#33 0x0000000000408841 in main (argc=4, argv=0x7fffa242e338, envp=0x7fffa242e360) at /var/tmp/portage/kde-base/kdelibs-4.4.1-r1/work/kdelibs-4.4.1/kinit/kinit.cpp:1834

This bug may be a duplicate of or related to bug 182026.

Possible duplicates by query: bug 231169.

Reported using DrKonqi