diet colitis flare up

I bought DKS today from Steam and upon Installing it i started it to play but Alas theres a big problem to me. the characters along with the World generally speaking wont show, all i buy is often a black screen on the other hand can see the mini-map as well as the windows tho ..... this is very weird! i attempted to play using the various Video options but nothing works! i can easily see the Cinematics fine tho but right that i start playing i cant begin to see the world whatsoever. anyone got ideas what could be the challenge? My video card is often a Geforce Gts 250 i play under Vista 64x