open quit working on mac g4

open gl stopped working on my mac g4 (rage 128 card). does anyone know
might cause this and how i can fix it?
i had turned virtual memory off, but after discovering that no opengl
games worked, turned it back on again. after that didnt work, i
reistalled opengl. still, no go. i tried rebuilding the desktop, and
zapping pram, but none of the game can even see opengl. (tomb raider
thinks its not there). it could be that something else entirely is
giving me problems.
rim vilgalys