Doom 3 graphical problems

I am running Doom 3 1.1b for mac on OS X leopard. My hardware:

1x 1.5Ghz G4
1.25 Gb DDR
Radeon 9000 64mb AGP
Built In MDD sound

When I run Doom, I get to the menu, but the mars planet is a white blob. start a game? The models, rooms and vehicles all lack textures.

Runs fine on my Intel machine.

Regards.

Looks like I need a 9700 or higher video card, rereading everything. Maybe the Doom3 to Doom2 mod will work?

Runs fine on my Powerbook though! All hail ATi!