Gammy

ok so doom 3 should work on my computer without a doubt. 3.4 ghz, 1 gig of ram dual highway, 128 ati 9700. i have directx 9.0c, and my latest video drivers. The game will run fine till i get to one certain point in the game and then it freezes. Mind you i am running the game on medium graphics on 800 x 600. I couldn't tell you what the problem is. If anyone has any help for me that would be fantastic. THanks a ton