Had this same problem until I loaded the restricted-modules package that corresponded to the kernel version I'm running. Now 3d apps doesn't hang the system any more.
-- Screensaver freezes on Dapper (ATI Radeon 8500 LE) https://launchpad.net/bugs/38181 -- desktop-bugs mailing list desktop-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/desktop-bugs
