The complete freeze happens with my Thinkpad x32 as well. Usually after 30 minutes or more of use, and not related to any particular program (or so it seems)
-- [dapper] xrandr freezes the system (radeon, MergedFB) https://launchpad.net/bugs/47775 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
