Version:            (using Devel)
Installed from:    Compiled sources
OS:                Linux

Well I do see other bugs of this sort posted, but this is with a recent SVN and so far has rendered my kde4 unusable.
Basically, I just log in and the first thing I see is the notify screen with a backtrace on a plasma crash. This started happening yesterday and so far its repeatable and consistently crashes.  Ive tried updating my builds but no fix has come down the pipes yet.
Its a user-built and run Kde4 (as per techbase).
Heres the backtrace:

Application: Plasma Workspace (plasma), signal SIGSEGV
Using host libthread_db library "/lib/tls/i686/cmov/libthread_db.so.1".
[Thread debugging using libthread_db enabled]
[New Thread -1250248128 (LWP 5417)]
[New Thread -1278899312 (LWP 5426)]
[KCrash handler]
#6  0x0369001f in ?? ()
#7  0xb7067249 in QObject::disconnect (sender=0x814bfe8, 
    signal=0x82dfe78 "2deviceAdded(QString)", receiver=0x82cd4a0, 
    method=0x8358019 "deviceAdded(QString)")
    at /home/kde-devel/kdesvn/qt-copy/src/corelib/kernel/qobject.cpp:2565
#8  0xb2a83604 in ~SolidDeviceEngine (this=0x82cd4a0)
    at /home/kde-devel/kdesvn/kdebase/workspace/plasma/dataengines/soliddevice/soliddeviceengine.cpp:64
#9  0xb7e89907 in ~DataEngineManager (this=0x83125d0)
    at /home/kde-devel/kdesvn/kdebase/workspace/libs/plasma/dataenginemanager.cpp:53
#10 0xb7e89bba in destroy ()
    at /home/kde-devel/kdesvn/kdebase/workspace/libs/plasma/dataenginemanager.cpp:73
#11 0xb7e891d8 in __tcf_0 () at /home/kde-devel/kde/include/kglobal.h:65
#12 0xb6509594 in exit () from /lib/tls/i686/cmov/libc.so.6
#13 0xb6f7defc in qt_message_output (msgType=QtFatalMsg, 
    buf=0xbfa39f1c "ASSERT: \"index.isValid()\" in file /home/kde-devel/kdesvn/kdebase/workspace/plasma/applets/devicenotifier/devicenotifier.cpp, line 297")
    at /home/kde-devel/kdesvn/qt-copy/src/corelib/global/qglobal.cpp:2049
#14 0xb6f7dfa8 in qFatal (msg=0xb709d4b0 "ASSERT: \"%s\" in file %s, line %d")
    at /home/kde-devel/kdesvn/qt-copy/src/corelib/global/qglobal.cpp:2249
#15 0xb6f7e055 in qt_assert (assertion=0xb2ac1967 "index.isValid()", 
    file=0xb2ac15c0 "/home/kde-devel/kdesvn/kdebase/workspace/plasma/applets/devicenotifier/devicenotifier.cpp", line=297)
    at /home/kde-devel/kdesvn/qt-copy/src/corelib/global/qglobal.cpp:1821
#16 0xb2abdab7 in DeviceNotifier::dataUpdated (this=0x80c7340, 
    source=@0xbfa3c374, data=@0xbfa3c268)
    at /home/kde-devel/kdesvn/kdebase/workspace/plasma/applets/devicenotifier/devicenotifier.cpp:297
#17 0xb2abe8d7 in DeviceNotifier::qt_metacall (this=0x80c7340, 
    _c=QMetaObject::InvokeMetaMethod, _id=2, _a=0xbfa3c328)
    at /home/kde-devel/kdesvn/build/kdebase/workspace/plasma/applets/devicenotifier/devicenotifier.moc:86
#18 0xb7063e5a in QMetaObject::activate (sender=0x830c9a0, 
    from_signal_index=<value optimized out>, to_signal_index=4, 
    argv=<value optimized out>)
    at /home/kde-devel/kdesvn/qt-copy/src/corelib/kernel/qobject.cpp:3001
#19 0xb7064252 in QMetaObject::activate (sender=0x830c9a0, m=0xb7f320d8, 
    local_signal_index=0, argv=0xbfa3c328)
    at /home/kde-devel/kdesvn/qt-copy/src/corelib/kernel/qobject.cpp:3074
#20 0xb7e83c39 in Plasma::DataContainer::dataUpdated (this=0x830c9a0, 
    _t1=@0xbfa3c374, _t2=@0x8343580)
    at /home/kde-devel/kdesvn/build/kdebase/workspace/libs/plasma/datacontainer.moc:94
#21 0xb7e8411d in Plasma::DataContainer::checkForUpdate (this=0x830c9a0)
    at /home/kde-devel/kdesvn/kdebase/workspace/libs/plasma/datacontainer.cpp:75
#22 0xb7e86c3e in Plasma::DataEngine::checkForUpdates (this=0x82cd4a0)
    at /home/kde-devel/kdesvn/kdebase/workspace/libs/plasma/dataengine.cpp:523
#23 0xb7e877cc in Plasma::DataEngine::qt_metacall (this=0x82cd4a0, 
    _c=QMetaObject::InvokeMetaMethod, _id=2, _a=0xbfa3c488)
    at /home/kde-devel/kdesvn/build/kdebase/workspace/libs/plasma/dataengine.moc:108
#24 0xb2a8422a in SolidDeviceEngine::qt_metacall (this=0x82cd4a0, 
    _c=QMetaObject::InvokeMetaMethod, _id=6, _a=0xbfa3c488)
    at /home/kde-devel/kdesvn/build/kdebase/workspace/plasma/dataengines/soliddevice/soliddeviceengine.moc:66
#25 0xb7063e5a in QMetaObject::activate (sender=0x82cd698, 
    from_signal_index=<value optimized out>, to_signal_index=4, 
    argv=<value optimized out>)
    at /home/kde-devel/kdesvn/qt-copy/src/corelib/kernel/qobject.cpp:3001
#26 0xb7064252 in QMetaObject::activate (sender=0x82cd698, m=0xb70f0ca4, 
    local_signal_index=0, argv=0x0)
    at /home/kde-devel/kdesvn/qt-copy/src/corelib/kernel/qobject.cpp:3074
#27 0xb709ca17 in QTimer::timeout (this=0x82cd698)
    at .moc/release-shared/moc_qtimer.cpp:126
#28 0xb706ca9e in QTimer::timerEvent (this=0x82cd698, e=0xbfa3c988)
    at /home/kde-devel/kdesvn/qt-copy/src/corelib/kernel/qtimer.cpp:263
#29 0xb7062ec5 in QObject::event (this=0x82cd698, e=0xbfa3c988)
    at /home/kde-devel/kdesvn/qt-copy/src/corelib/kernel/qobject.cpp:1105
#30 0xb6889f7f in QApplicationPrivate::notify_helper (this=0x807b458, 
    receiver=0x82cd698, e=0xbfa3c988)
    at /home/kde-devel/kdesvn/qt-copy/src/gui/kernel/qapplication.cpp:3735
#31 0xb6890899 in QApplication::notify (this=0x80622c0, receiver=0x82cd698, 
    e=0xbfa3c988)
    at /home/kde-devel/kdesvn/qt-copy/src/gui/kernel/qapplication.cpp:3329
#32 0xb761f63a in KApplication::notify (this=0x80622c0, receiver=0x82cd698, 
    event=0xbfa3c988)
    at /home/kde-devel/kdesvn/kdelibs/kdeui/kernel/kapplication.cpp:311
#33 0xb7053979 in QCoreApplication::notifyInternal (this=0x80622c0, 
    receiver=0x82cd698, event=0xbfa3c988)
    at /home/kde-devel/kdesvn/qt-copy/src/corelib/kernel/qcoreapplication.cpp:582
#34 0xb707bdfd in QTimerInfoList::activateTimers (this=0x807e214)
    at ../../include/QtCore/../../../../qt-copy/src/corelib/kernel/qcoreapplication.h:215
#35 0xb7079780 in timerSourceDispatch (source=0x807e1e0)
    at /home/kde-devel/kdesvn/qt-copy/src/corelib/kernel/qeventdispatcher_glib.cpp:166
#36 0xb62f011c in g_main_context_dispatch () from /usr/lib/libglib-2.0.so.0
#37 0xb62f355f in ?? () from /usr/lib/libglib-2.0.so.0
#38 0x0807d4b0 in ?? ()
#39 0x00000000 in ?? ()
#0  0xffffe410 in __kernel_vsyscall ()