metacity crashes and xinerama reconfigures screens

[Martin Weis]

I have regular flickering screens (xinerama re-initialises them) in a dual-screen setup under gnome-2d, as can be seen in .xsession-errors and Xorg.0.log.
Sometimes metacity crashes then, as it was the case recently, when I had verbose logging-mode on.

Last 1000 lines of the log before the crash are here:
http://paste.ubuntu.com/1373239/
Line 764 looks to me like the reconfiguration due to a 'flicker'.

Console output of metacity (started from there with METACITY_VERBOSE=1 METACITY_USE_LOGFILE=1 metacity --replace)
metacity:ERROR:core/boxes.c:1165:meta_rectangle_edge_aligns: code should not be reached

and there is
/var/crash/_usr_bin_metacity.1000.crash

which I will attach.

I do not know, if the two problems are really related (metacity crash, xinerama re-init), but it looked like (happened at the same time).
Any debugging hints to find the reason for the xinerama re-init are welcome. Sometimes it is impossible to work due to high frequency of re-inits.

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: metacity 1:2.34.1-1ubuntu11
ProcVersionSignature: Ubuntu 3.2.0-33.52-generic 3.2.31
Uname: Linux 3.2.0-33-generic x86_64
NonfreeKernelModules: openafs
ApportVersion: 2.0.1-0ubuntu15
Architecture: amd64
Date: Tue Nov 20 21:35:24 2012
InstallationMedia: Ubuntu 11.10 "Oneiric Ocelot" - Release amd64 (20111012)
MarkForUpload: True
SourcePackage: metacity
UpgradeStatus: Upgraded to precise on 2012-10-08 (43 days ago)