kwin crashed with SIGABRT in __assert_fail_base()

[Riddick]

Unfortunately I cannot provide further infos because it was my wife who has been near the laptop during this crash...I've simply noticed only the crash afterwards.
I decided to submit this crash report...maybe it can be fixed anyway.

ProblemType: Crash
DistroRelease: Ubuntu 12.04
Package: kde-window-manager 4:4.8.0b-0ubuntu5
ProcVersionSignature: Ubuntu 3.2.0-17.27-generic-pae 3.2.6
Uname: Linux 3.2.0-17-generic-pae i686
NonfreeKernelModules: nvidia
ApportVersion: 1.94-0ubuntu1
Architecture: i386
Date: Sun Mar 4 16:56:23 2012
ExecutablePath: /usr/bin/kwin
InstallationMedia: Kubuntu 12.04 LTS "Precise Pangolin" - Beta i386 (20120228.1)
ProcCmdline: /usr/bin/kwin --crashes 1
ProcEnviron:
 LANGUAGE=
 LANG=en_US.UTF-8
 SHELL=/bin/bash
Signal: 6
SourcePackage: kde-workspace
StacktraceTop:
 raise () from /lib/i386-linux-gnu/libc.so.6
 abort () from /lib/i386-linux-gnu/libc.so.6
 ?? () from /lib/i386-linux-gnu/libc.so.6
 __assert_fail () from /lib/i386-linux-gnu/libc.so.6
 _XAllocID () from /usr/lib/i386-linux-gnu/libX11.so.6
Title: kwin crashed with SIGABRT in raise()
UpgradeStatus: No upgrade log present (probably fresh install)
UserGroups: adm cdrom dip lpadmin plugdev sambashare sudo

[Apport retracing service (apport)]

StacktraceTop:
 __assert_fail_base (fmt=0xb75ad438 "%s%s%s:%u: %s%sAssertion `%s' failed.\n%n", assertion=0xb6847d79 "ret != inval_id", file=0xb6847cea "../../src/xcb_io.c", line=528, function=0xb6847dfe "_XAllocID") at assert.c:94
 __GI___assert_fail (assertion=0xb6847d79 "ret != inval_id", file=0xb6847cea "../../src/xcb_io.c", line=528, function=0xb6847dfe "_XAllocID") at assert.c:103
 _XAllocID (dpy=0x8f83760) at ../../src/xcb_io.c:528
 XRenderCreatePicture (dpy=0x8f83760, drawable=31457285, format=0x8f85098, valuemask=0, attributes=0x0) at ../../src/Picture.c:90
 QX11PixmapData::x11ConvertToDefaultDepth (this=0x904ebd8) at image/qpixmap_x11.cpp:2255