i just got the copy from quakecon sale

i have xfx ati radeon 6670, and amd phenom 2 820 quad-core, win 7 64bit.

i try to start lost mission and it would not play. i have verify instalation idk if that will help but doing now. i have not tired any other modes but idk what is wrong with it.

edit only doom 3 does doom 1 and 2 work fine. i am also contacting steam support.