Game Engine Keeps Crashing

[fenderlonestar]

hi
I have just purchased penumbra black plague and was really looking forward to playing it, as i have been a big fan of the penumbra series. However much to my surprise the textures, particles and lighting where all stuffing up. (The reason i was surpised is i am running a pc 4.1 Ghz cpu, ATi 4870x2, 8gb Ram) i downloaded the patch and that fised the texture problems but the game crashes pretty much every time i go through a door which requires a load. Also i cant select vsync in my advanced graphics settings, the game crashes every time i retry. I have installed the latest drivers on my card and reinstalled penumbra twice already. The funny thing is that my old pc (2.8ghz P4, 512 mb RAM and a nvidia FX5200) ran oveture and the tech demo fine, no glitches at all.
IF someone could please help me, it would be greatly appreciated as i would love to enjoy the penumbra experiance with maximum graphics
cheers
liam