System: K6-2/450, 324 Mb RAM, Voodoo3 3000AGP 16Mb vidcard
Distro: Mandrake 7.0 , latest Glide and XFree86 3.3.6
When quitting game, after you click "yes" when it asks you if you really want to leave, the screen switches back to the "gaming" scene you were in last, and stays that way. ALT-CTRL-BACKSPACE will dump X, but the screen does not change. Rebooting is the only way I found to clear it.
Workaround: I have found that hitting F10 at the menu screen will cause an immediate segfault and get me back into X. This is my means of exit for now ;-)