Comment 10 for bug 1507764

I just had again the same crash. :
Dec 30 23:49:59 archer gnome-session[28277]: Window manager warning: Log level 6: The program 'metacity' received an X Window System error.
Dec 30 23:49:59 archer gnome-session[28277]: This probably reflects a bug in the program.
Dec 30 23:49:59 archer gnome-session[28277]: The error was 'BadRegion (invalid Region parameter)'.
Dec 30 23:49:59 archer gnome-session[28277]: (Details: serial 1686054464 error_code 140 request_code 138 (XFIXES) minor_code 12)
Dec 30 23:49:59 archer gnome-session[28277]: (Note to programmers: normally, X errors are reported asynchronously;
Dec 30 23:49:59 archer gnome-session[28277]: that is, you will receive the error a while after causing it.
Dec 30 23:49:59 archer gnome-session[28277]: To debug your program, run it with the GDK_SYNCHRONIZE environment
Dec 30 23:49:59 archer gnome-session[28277]: variable to change this behavior. You can then get a meaningful
Dec 30 23:49:59 archer gnome-session[28277]: backtrace from your debugger if you break on the gdk_x_error() function.)

which led once apport was done writing the crash report :
Dec 30 23:54:51 archer gnome-session[28277]: gnome-session[28277]: WARNING: Application 'metacity.desktop' killed by signal 5
Dec 30 23:54:51 archer gnome-session[28277]: WARNING: Application 'metacity.desktop' killed by signal 5
Dec 30 23:54:51 archer gnome-session[28277]: gnome-session[28277]: WARNING: App 'metacity.desktop' respawning too quickly
Dec 30 23:54:51 archer gnome-session[28277]: WARNING: App 'metacity.desktop' respawning too quickly
Dec 30 23:54:51 archer gnome-session[28277]: Unrecoverable failure in required component metacity.desktop
Dec 30 23:54:51 archer gnome-session[28277]: gnome-session[28277]: CRITICAL: We failed, but the fail whale is dead. Sorry....
Dec 30 23:54:51 archer gnome-session[28277]: CRITICAL: We failed, but the fail whale is dead. Sorry....

From what I tried, it seems like trying to run "metacity --replace" before apport finishes killing the old instance does not work : once it freezes and apport is writing its stuff, the whole session will go down.

Seriously, this regression is infuriating and makes Ubuntu barely usable for me.
I nearly stopped using Alt+Tab out of fear of losing work when switching between gedit and evince.