Please report to the developers of the "yasp" plasma widget that using 349 threads is just insane.

Pasting the main thread only for easing duplicate search:

Thread 1 (Thread 0xb1bb7720 (LWP 2890)):
[KCrash Handler]
#7  pageTableSize (this=0x933e498, key=..., data=...) at ../../kdecore/util/kshareddatacache.cpp:431
#8  indexTableSize (this=0x933e498, key=..., data=...) at ../../kdecore/util/kshareddatacache.cpp:438
#9  KSharedDataCache::insert (this=0x933e498, key=..., data=...) at ../../kdecore/util/kshareddatacache.cpp:1234
#10 0xb6d55b33 in KIconLoaderPrivate::insertCachedPixmapWithPath (this=0x8309938, key=..., data=..., path=...) at ../../kdeui/icons/kiconloader.cpp:840
#11 0xb6d5d587 in KIconLoader::loadIcon (this=0x94a7988, _name=..., group=KIconLoader::Desktop, size=48, state=0, overlays=..., path_store=0x0, canReturnNull=false) at ../../kdeui/icons/kiconloader.cpp:1318
#12 0xb6d53ba9 in KIconEngine::pixmap (this=0x94d1bf0, size=..., mode=QIcon::Normal, state=QIcon::Off) at ../../kdeui/icons/kiconengine.cpp:93
#13 0xb5d3cc76 in QIcon::pixmap (this=0xbffe27e0, size=..., mode=QIcon::Normal, state=QIcon::Off) at image/qicon.cpp:676
#14 0xb759d183 in pixmap (this=0xbffe25d8, mainText=..., subText=..., icon=...) at /usr/include/qt4/QtGui/qicon.h:80
#15 Plasma::ToolTipContent::ToolTipContent (this=0xbffe25d8, mainText=..., subText=..., icon=...) at ../../plasma/tooltipcontent.cpp:106
#16 0xa9ecefe8 in ?? () from /usr/lib/kde4/plasma_applet_systemtray.so
#17 0xa9ed1953 in ?? () from /usr/lib/kde4/plasma_applet_systemtray.so
#18 0xa9ed2be6 in ?? () from /usr/lib/kde4/plasma_applet_systemtray.so
#19 0xb677b44a in QMetaObject::metacall (object=0x94907e8, cl=156187008, idx=155781096, argv=0xa) at kernel/qmetaobject.cpp:237
#20 0xb678e035 in QMetaObject::activate (sender=0x94b5958, m=0xb769dc44, local_signal_index=0, argv=0xbffe2974) at kernel/qobject.cpp:3272
#21 0xb74ea2d9 in Plasma::DataContainer::dataUpdated (this=0x94b5958, _t1=..., _t2=...) at ./datacontainer.moc:101
#22 0xb74ea458 in Plasma::DataContainer::checkForUpdate (this=0x94b5958) at ../../plasma/datacontainer.cpp:169
#23 0xa9ea3bf6 in ?? () from /usr/lib/kde4/plasma_engine_statusnotifieritem.so
#24 0xa9ea6d5f in ?? () from /usr/lib/kde4/plasma_engine_statusnotifieritem.so
#25 0xb677b44a in QMetaObject::metacall (object=0x94b5958, cl=156187008, idx=155933016, argv=0xbffe2d54) at kernel/qmetaobject.cpp:237
#26 0xb678e035 in QMetaObject::activate (sender=0x94ce610, m=0xb69245a4, local_signal_index=0, argv=0xbffe2eb8) at kernel/qobject.cpp:3272
#27 0xb69096c3 in QDBusPendingCallWatcher::finished (this=0x94ce610, _t1=0x94ce610) at .moc/release-shared/moc_qdbuspendingcall.cpp:92
#28 0xb690975a in _q_finished (this=0x94ce610, _c=QMetaObject::InvokeMetaMethod, _id=5, _a=0x94a69d0) at qdbuspendingcall.cpp:482
#29 QDBusPendingCallWatcher::qt_metacall (this=0x94ce610, _c=QMetaObject::InvokeMetaMethod, _id=5, _a=0x94a69d0) at .moc/release-shared/moc_qdbuspendingcall.cpp:80
#30 0xb677b44a in QMetaObject::metacall (object=0x94ce610, cl=156187008, idx=5, argv=0x94a69d0) at kernel/qmetaobject.cpp:237
#31 0xb6786796 in QMetaCallEvent::placeMetaCall (this=0x94958a0, object=0x94ce610) at kernel/qobject.cpp:534
#32 0xb67878c2 in QObject::event (this=0x94ce610, e=0x0) at kernel/qobject.cpp:1211
#33 0xb5c78c6c in QApplicationPrivate::notify_helper (this=0x820b8b0, receiver=0x94ce610, e=0x94958a0) at kernel/qapplication.cpp:4445
#34 0xb5c7e6ce in QApplication::notify (this=0x81fa080, receiver=0x94ce610, e=0x94958a0) at kernel/qapplication.cpp:3845
#35 0xb6da9caa in KApplication::notify (this=0x81fa080, receiver=0x94ce610, event=0x94958a0) at ../../kdeui/kernel/kapplication.cpp:310
#36 0xb677577b in QCoreApplication::notifyInternal (this=0x81fa080, receiver=0x94ce610, event=0x94958a0) at kernel/qcoreapplication.cpp:732
#37 0xb677897c in sendEvent (receiver=0x0, event_type=0, data=0x81a6010) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:215
#38 QCoreApplicationPrivate::sendPostedEvents (receiver=0x0, event_type=0, data=0x81a6010) at kernel/qcoreapplication.cpp:1373
#39 0xb6778add in QCoreApplication::sendPostedEvents (receiver=0x0, event_type=0) at kernel/qcoreapplication.cpp:1266
#40 0xb67a4294 in sendPostedEvents (s=0x8211110) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:220
#41 postEventSourceDispatch (s=0x8211110) at kernel/qeventdispatcher_glib.cpp:277
#42 0xb3b5c305 in g_main_context_dispatch () from /lib/libglib-2.0.so.0
#43 0xb3b5ffe8 in ?? () from /lib/libglib-2.0.so.0
#44 0xb3b601c8 in g_main_context_iteration () from /lib/libglib-2.0.so.0
#45 0xb67a3d85 in QEventDispatcherGlib::processEvents (this=0x81a5cd0, flags=...) at kernel/qeventdispatcher_glib.cpp:415
#46 0xb5d3a305 in QGuiEventDispatcherGlib::processEvents (this=0x81a5cd0, flags=...) at kernel/qguieventdispatcher_glib.cpp:204
#47 0xb6774229 in QEventLoop::processEvents (this=0xbffe36f4, flags=) at kernel/qeventloop.cpp:149
#48 0xb67746aa in QEventLoop::exec (this=0xbffe36f4, flags=...) at kernel/qeventloop.cpp:201
#49 0xb6778b9f in QCoreApplication::exec () at kernel/qcoreapplication.cpp:1009
#50 0xb5c77c27 in QApplication::exec () at kernel/qapplication.cpp:3719
#51 0xb784d64e in kdemain () from /usr/lib/kde4/libkdeinit/libkdeinit4_plasma-desktop.so
#52 0x0804861b in _start ()

Possibly the icon and Plasma theme caches are corrupt, especially if you've had earlier versions of KDE 4.5 series installed earlier.

A possible workaround is to delete the *.kcache files that are normally in /var/tmp/kdecache-$USER/*.kcache. You can find the exact directory by running the "kde4-config --path cache" command at a terminal. It is safe to delete *.kcache files in this directory even if KDE is already running, but you would need to restart KDE for that deletion to fully take effect.

Please note that the upcoming 4.6 release has fixed an additional bug with KSharedDataCache (with 4.5.4 after resetting the caches, you may get warning messages about the cache possibly being corrupt, but it shouldn't crash)

Please let me know if the workaround helps, and if the bug you are having persists in the 4.6 release when it happens (and note that the bugfix I'm referring to is /very recent/, it was not part of any 4.6 release candidate).

after both removing the yasp widget and deleting the icon cache I haven't been able to reproduce the bug anymore