This is also a big problem for me.
Using ubuntu 12.10 i386 and amd64, both fully updated final releases, both are affected both have very different hardware.
I have gnome-shell installed but it also happens in the unity desktop too!
I have been unable to simply restart gnome-shell as it either reappears with no window manager again or locks up trying to start it again.
I have to ultimately reboot the computers to recover, very tedious and annoying, let me know if I can help with debugging this and finding a fix.
Cheers Swampy.
This is also a big problem for me.
Using ubuntu 12.10 i386 and amd64, both fully updated final releases, both are affected both have very different hardware.
I have gnome-shell installed but it also happens in the unity desktop too!
I have been unable to simply restart gnome-shell as it either reappears with no window manager again or locks up trying to start it again.
I have to ultimately reboot the computers to recover, very tedious and annoying, let me know if I can help with debugging this and finding a fix.
Cheers Swampy.