Version:            (using KDE 4.2.0)
OS:                Linux
Installed from:    Ubuntu Packages

I have a dual-monitor setup (dell laptop and dell external monitor), using nvidia M120 card (or N120?). When I drag an application window from one monitor to the other, the screen freezes for a second and I get a popup about KWin crashing. Here is the backtrace from the crash handler:

Application: KWin (kwin), signal SIGABRT

Thread 1 (Thread 0xb57626e0 (LWP 13692)):
[KCrash Handler]
#6  0xb8077430 in __kernel_vsyscall ()
#7  0xb692c880 in raise () from /lib/tls/i686/cmov/libc.so.6
#8  0xb692e248 in abort () from /lib/tls/i686/cmov/libc.so.6
#9  0xb6dd6795 in qt_message_output () from /usr/lib/libQtCore.so.4
#10 0xb6dd6872 in qFatal () from /usr/lib/libQtCore.so.4
#11 0xb6dd68cc in qt_assert_x () from /usr/lib/libQtCore.so.4
#12 0xb7fff01a in ?? () from /usr/lib/libkdeinit4_kwin.so
#13 0xb7fff2cf in ?? () from /usr/lib/libkdeinit4_kwin.so
#14 0xb80051fd in ?? () from /usr/lib/libkdeinit4_kwin.so
#15 0xb7fdb7ac in ?? () from /usr/lib/libkdeinit4_kwin.so
#16 0xb7fdc485 in ?? () from /usr/lib/libkdeinit4_kwin.so
#17 0xb7fdce6a in ?? () from /usr/lib/libkdeinit4_kwin.so
#18 0xb7fc8d52 in ?? () from /usr/lib/libkdeinit4_kwin.so
#19 0xb71bea9e in ?? () from /usr/lib/libQtGui.so.4
#20 0xb71cf4d5 in QApplication::x11ProcessEvent () from /usr/lib/libQtGui.so.4
#21 0xb71fa7aa in ?? () from /usr/lib/libQtGui.so.4
#22 0xb66b56f8 in g_main_context_dispatch () from /usr/lib/libglib-2.0.so.0
#23 0xb66b8da3 in ?? () from /usr/lib/libglib-2.0.so.0
#24 0xb66b8f61 in g_main_context_iteration () from /usr/lib/libglib-2.0.so.0
#25 0xb6ef9478 in QEventDispatcherGlib::processEvents () from /usr/lib/libQtCore.so.4
#26 0xb71f9ea5 in ?? () from /usr/lib/libQtGui.so.4
#27 0xb6ecd52a in QEventLoop::processEvents () from /usr/lib/libQtCore.so.4
#28 0xb6ecd6ea in QEventLoop::exec () from /usr/lib/libQtCore.so.4
#29 0xb6ecfda5 in QCoreApplication::exec () from /usr/lib/libQtCore.so.4
#30 0xb715f767 in QApplication::exec () from /usr/lib/libQtGui.so.4
#31 0xb7fccce2 in kdemain () from /usr/lib/libkdeinit4_kwin.so
#32 0x08048732 in _start ()