I have 3 PowerMac 7.3 G5 @ 2Ghz

2 of them have a radeon 9600 Pro, the over have a radeon 9600XT.

All of them freeze playing Quake III Arena during the 10 first minutes of game.

The same game doesn't freeze on my PowerBook or Pegasos II. It's a PowerMac G5 issue.