I've got the same behavior today after second reboot since dist-upgrade on Thursday (2007-04-19).
There is a trace of it in my /var/log/apport.log:
apport (pid 8871) Fri Apr 20 10:29:40 2007: executable: /usr/bin/metacity (command line "metacity --sm-save-file 1176762446-5049-2391774710.ms")
apport (pid 8871) Fri Apr 20 10:29:42 2007: wrote report /var/crash/_usr_bin_metacity.1000.crash
I've got the same behavior today after second reboot since dist-upgrade on Thursday (2007-04-19).
There is a trace of it in my /var/log/ apport. log: 5049-2391774710 .ms") _usr_bin_ metacity. 1000.crash
apport (pid 8871) Fri Apr 20 10:29:40 2007: executable: /usr/bin/metacity (command line "metacity --sm-save-file 1176762446-
apport (pid 8871) Fri Apr 20 10:29:42 2007: wrote report /var/crash/
I'm attaching the crash report.