Version:            (using Devel)
Compiler:          gcc 4.4.1 [gcc-4_4-branch revision 150839] (SUSE Linux) 
OS:                Linux
Installed from:    Compiled sources

svn version of kdelibs: 1117720

if i create a KCategorizedView and is not either in icon mode (like systemsettings)
or the verticalScrollMode is not QListView::ScrollPerPixel, after the list is scrolled, it can be either badly drawn or crash, hitting an assert.
A simple way to trigger this is to apply this patch on the systray plasma applet:

Index: workspace/plasma/generic/applets/systemtray/ui/applet.cpp
===================================================================
--- workspace/plasma/generic/applets/systemtray/ui/applet.cpp   (revision 1117718)
+++ workspace/plasma/generic/applets/systemtray/ui/applet.cpp   (working copy)
@@ -481,7 +481,6 @@
 
         m_plasmoidTasksUi.visibleItemsView->setCategoryDrawer(new KCategoryDrawerV3(m_plasmoidTasksUi.visibleItemsView));
         m_plasmoidTasksUi.visibleItemsView->setMouseTracking(true);
-        m_plasmoidTasksUi.visibleItemsView->setVerticalScrollMode(QListView::ScrollPerPixel);
 
         KCategorizedSortFilterProxyModel *visibleItemsModel = new KCategorizedSortFilterProxyModel();
 


this is the backtrace:
the view seems to scroll "too much", after all the items go offscreen this crash is produced. i guess the view is attempting to fetch a modelitem out of boundaries.
this happens only if the model has been set as categorizedmodel and the view had a categorydrawer set

Application: Plasma Widget Viewer (plasmoidviewer), signal: Aborted
[Current thread is 1 (Thread 0xb259d720 (LWP 6615))]

Thread 2 (Thread 0xa6e8eb70 (LWP 6616)):
#0  0xffffe424 in __kernel_vsyscall ()
#1  0xb6aea0c2 in pthread_cond_timedwait@@GLIBC_2.3.2 () from /lib/libpthread.so.0
#2  0xb6b688ad in QWaitConditionPrivate::wait (this=0x8473818, time=30000) at thread/qwaitcondition_unix.cpp:85
#3  0xb6b686cb in QWaitCondition::wait (this=0x847377c, mutex=0x8473778, time=30000) at thread/qwaitcondition_unix.cpp:159
#4  0xb6b5ac0e in QThreadPoolThread::run (this=0x82877f0) at concurrent/qthreadpool.cpp:140
#5  0xb6b6764f in QThreadPrivate::start (arg=0x82877f0) at thread/qthread_unix.cpp:248
#6  0xb6ae56e5 in start_thread () from /lib/libpthread.so.0
#7  0xb6ae5600 in ?? () from /lib/libpthread.so.0

Thread 1 (Thread 0xb259d720 (LWP 6615)):
[KCrash Handler]
#7  0xffffe424 in __kernel_vsyscall ()
#8  0xb5ced0cf in raise () from /lib/libc.so.6
#9  0xb5cee9e7 in abort () from /lib/libc.so.6
#10 0xb6b5da20 in qt_message_output (msgType=QtFatalMsg, buf=
    0x84106b8 "ASSERT failure in QVector<T>::at: \"index out of range\", file ../../include/QtCore/../../src/corelib/tools/qvector.h, line 338") at global/qglobal.cpp:2248
#11 0xb6b5dac6 in qt_message (msgType=QtFatalMsg, msg=0xb6cd6648 "ASSERT failure in %s: \"%s\", file %s, line %d", ap=0xbfc7e3d4 "\271A\201\266\217A\201\266XA\201\266R\001")
    at global/qglobal.cpp:2294
#12 0xb6b5ddbc in qFatal (msg=0xb6cd6648 "ASSERT failure in %s: \"%s\", file %s, line %d") at global/qglobal.cpp:2477
#13 0xb6b5d681 in qt_assert_x (where=0xb68141b9 "QVector<T>::at", what=0xb681418f "index out of range", file=0xb6814158 "../../include/QtCore/../../src/corelib/tools/qvector.h", line=338)
    at global/qglobal.cpp:2019
#14 0xb60e9011 in QVector<int>::at (this=0x83cb85c, i=11) at ../../include/QtCore/../../src/corelib/tools/qvector.h:338
#15 0xb66a3de7 in QListModeViewBase::verticalOffset (this=0x83cb830) at itemviews/qlistview.cpp:2108
#16 0xb669ec4f in QListView::verticalOffset (this=0x83ac998) at itemviews/qlistview.cpp:1096
#17 0xb668b9a7 in QAbstractItemViewPrivate::contentsOffset (this=0x82f49e0) at ../../include/QtGui/private/../../../src/gui/itemviews/qabstractitemview_p.h:294
#18 0xb611330d in QWidgetPrivate::paintBackground (this=0x83ac9b8, painter=0xbfc7e5e8, rgn=..., flags=0) at kernel/qwidget.cpp:2197
#19 0xb6119d33 in QWidgetPrivate::drawWidget (this=0x83ac9b8, pdev=0x8357434, rgn=..., offset=..., flags=4, sharedPainter=0x0, backingStore=0x83573f8) at kernel/qwidget.cpp:5337
#20 0xb630276c in QWidgetBackingStore::sync (this=0x83573f8) at painting/qbackingstore.cpp:1292
#21 0xb611165f in QWidgetPrivate::syncBackingStore (this=0x83ef068) at kernel/qwidget.cpp:1684
#22 0xb61212c5 in QWidget::event (this=0x83aa538, event=0x83ff5a0) at kernel/qwidget.cpp:8333
#23 0xb60bfb2a in QApplicationPrivate::notify_helper (this=0x808eb40, receiver=0x83aa538, e=0x83ff5a0) at kernel/qapplication.cpp:4302
#24 0xb60bf990 in QApplication::notify (this=0xbfc7f2ac, receiver=0x83aa538, e=0x83ff5a0) at kernel/qapplication.cpp:4267
#25 0xb761b7d0 in KApplication::notify (this=0xbfc7f2ac, receiver=0x83aa538, event=0x83ff5a0) at /home/diau/svn/KDE/kdelibs/kdeui/kernel/kapplication.cpp:302
#26 0xb6c655ba in QCoreApplication::notifyInternal (this=0xbfc7f2ac, receiver=0x83aa538, event=0x83ff5a0) at kernel/qcoreapplication.cpp:704
#27 0xb6c6890f in QCoreApplication::sendEvent (receiver=0x83aa538, event=0x83ff5a0) at kernel/qcoreapplication.h:215
#28 0xb6c665e2 in QCoreApplicationPrivate::sendPostedEvents (receiver=0x0, event_type=0, data=0x80787e0) at kernel/qcoreapplication.cpp:1342
#29 0xb6c6629b in QCoreApplication::sendPostedEvents (receiver=0x0, event_type=0) at kernel/qcoreapplication.cpp:1238
#30 0xb6c979a0 in QCoreApplication::sendPostedEvents () at kernel/qcoreapplication.h:220
#31 0xb6c963a3 in postEventSourceDispatch (s=0x8090f20) at kernel/qeventdispatcher_glib.cpp:276
#32 0xb42494c2 in g_main_context_dispatch () from /usr/lib/libglib-2.0.so.0
#33 0xb424cd98 in ?? () from /usr/lib/libglib-2.0.so.0
#34 0xb424cebe in g_main_context_iteration () from /usr/lib/libglib-2.0.so.0
#35 0xb6c971dc in QEventDispatcherGlib::processEvents (this=0x808eb20, flags=...) at kernel/qeventdispatcher_glib.cpp:412
#36 0xb6181468 in QGuiEventDispatcherGlib::processEvents (this=0x808eb20, flags=...) at kernel/qguieventdispatcher_glib.cpp:204
#37 0xb6c63057 in QEventLoop::processEvents (this=0xbfc7f1ec, flags=...) at kernel/qeventloop.cpp:149
#38 0xb6c6319b in QEventLoop::exec (this=0xbfc7f1ec, flags=...) at kernel/qeventloop.cpp:197
#39 0xb6c65c60 in QCoreApplication::exec () at kernel/qcoreapplication.cpp:981
#40 0xb60bcffe in QApplication::exec () at kernel/qapplication.cpp:3581
#41 0x080513d8 in main (argc=4, argv=0xbfc7f5f4) at /home/diau/svn/KDE/kdebase/workspace/plasma/generic/shells/plasmoidviewer/main.cpp:231