Graphics problem with the Penumbra Collection

[OnscreenPiano38]

I bought the Penumbra Collection and I absolutely love the game. But I have an iBook G4 with Mac OSX 10.4.11 I turned the graphics and everything as low as I can. The problem is is that when I enter a larger area (rather than a smaller room) everything gets all flashy and I see black triangles flashing on and off. It is really annoying and would like some help. If this issue can't be fixed I understand and I will deal with it but I would appreciate a solution. Thank you guys.