Version:            (using Devel)
Compiler:           Project Neon nightly snapshot
OS:                Linux
Installed from:    Compiled sources

Similar to bug# 173017 however this trace went down a different path to the one there.

Using xrandr to enable 2nd monitor. 
Cmd: xrandr --output VGA --mode 1280x1024 --left-of LVDS

Backtrace:
Application: KWin (kwin), signal SIGABRT

Thread 1 (Thread 0xb66926c0 (LWP 6379)):
[KCrash Handler]
#6  0xb7f3e430 in __kernel_vsyscall ()
#7  0xb69f4880 in raise () from /lib/tls/i686/cmov/libc.so.6
#8  0xb69f6248 in abort () from /lib/tls/i686/cmov/libc.so.6
#9  0xb767851d in qt_message_output () from /opt/project-neon/lib/libQtCore.so.4
#10 0xb76785d2 in qFatal () from /opt/project-neon/lib/libQtCore.so.4
#11 0xb767862c in qt_assert_x () from /opt/project-neon/lib/libQtCore.so.4
#12 0xb7ee4ab5 in ?? () from /opt/kde-nightly/lib/libkdeinit4_kwin.so
#13 0xb7ed901b in ?? () from /opt/kde-nightly/lib/libkdeinit4_kwin.so
#14 0xb7ed929f in ?? () from /opt/kde-nightly/lib/libkdeinit4_kwin.so
#15 0xb7edbd8e in ?? () from /opt/kde-nightly/lib/libkdeinit4_kwin.so
#16 0xb7edd33b in ?? () from /opt/kde-nightly/lib/libkdeinit4_kwin.so
#17 0xb7ee1cf0 in ?? () from /opt/kde-nightly/lib/libkdeinit4_kwin.so
#18 0xb7eb58fc in ?? () from /opt/kde-nightly/lib/libkdeinit4_kwin.so
#19 0xb7eb660c in ?? () from /opt/kde-nightly/lib/libkdeinit4_kwin.so
#20 0xb776bf6a in QCoreApplicationPrivate::sendThroughObjectEventFilters () from /opt/project-neon/lib/libQtCore.so.4
#21 0xb6f496da in QApplicationPrivate::notify_helper () from /opt/project-neon/lib/libQtGui.so.4
#22 0xb6f51437 in QApplication::notify () from /opt/project-neon/lib/libQtGui.so.4
#23 0xb7ca0df3 in KApplication::notify (this=0xbff3df44, receiver=0x8b162f0, event=0xbff3d648) at /build/buildd/kde-nightly-kdelibs-20081202.7+svn891822/kdeui/kernel/kapplication.cpp:307
#24 0xb7ea83ca in ?? () from /opt/kde-nightly/lib/libkdeinit4_kwin.so
#25 0xb776c591 in QCoreApplication::notifyInternal () from /opt/project-neon/lib/libQtCore.so.4
#26 0xb6f5067a in QApplicationPrivate::sendMouseEvent () from /opt/project-neon/lib/libQtGui.so.4
#27 0xb6fb6fe0 in ?? () from /opt/project-neon/lib/libQtGui.so.4
#28 0xb6fb601b in QApplication::x11ProcessEvent () from /opt/project-neon/lib/libQtGui.so.4
#29 0xb6fddbda in ?? () from /opt/project-neon/lib/libQtGui.so.4
#30 0xb674c6f8 in g_main_context_dispatch () from /usr/lib/libglib-2.0.so.0
#31 0xb674fda3 in ?? () from /usr/lib/libglib-2.0.so.0
#32 0xb674ff61 in g_main_context_iteration () from /usr/lib/libglib-2.0.so.0
#33 0xb7795ea8 in QEventDispatcherGlib::processEvents () from /opt/project-neon/lib/libQtCore.so.4
#34 0xb6fdd2e5 in ?? () from /opt/project-neon/lib/libQtGui.so.4
#35 0xb776af9a in QEventLoop::processEvents () from /opt/project-neon/lib/libQtCore.so.4
#36 0xb776b15a in QEventLoop::exec () from /opt/project-neon/lib/libQtCore.so.4
#37 0xb77701fd in QCoreApplication::exec () from /opt/project-neon/lib/libQtCore.so.4
#38 0xb6f49427 in QApplication::exec () from /opt/project-neon/lib/libQtGui.so.4
#39 0xb7ea98ff in kdemain () from /opt/kde-nightly/lib/libkdeinit4_kwin.so
#40 0x08048792 in _start ()