I have a new G4 400 SP and I too have experienced the freeze problem when playing the demo. It seemed random initially so I tried all of the recommended trouble shooting procedures. It didn't seem to change much however, as I've gotten used to playing the game the number of freezes has almost ceased. I can't explain it.
I have the blacked out text problem and would like to try the Open GL 1.2.1. Could you possibly e-mail it to me? It would be much appreciated because I have to find out what's going on by using line of sight all the time!