I am also non-laptop, ATi 9600xt (lucky me eh?) this card has been a pita. But it isn't always locking up, it is random. Maybe 50/50 (no difference with ati or fglrx drivers) the x-server restart workaround has worked for me, but it's still not ideal.
-- Lockup problems with both the free xorg ATI driver and the proprietary fglrx driver, using various ATI cards https://launchpad.net/bugs/30447 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
