Prototype only runs in low resolutions

The game will not run on resolutions higher than 1280*800, which quite pisses me off, because I didn't buy my 1680*1050 monitor for nothing. The option just doesn't appear in the game, and I have tried several fixes from gamecopyworld, I've tried editing the enginef.dll file, I tried running in windowed mode, nothing worked.
I would really like to be able to run this game at my native resolution.
This problem is frequent with graphics cards with <500MB VRAM.
I however, have 2GB of VRAM, so that shouldn't be the problem.

System:
MSI k9a2 cf-f (mobo)
Powercolor HD4850 2GB (graphics)
AMD Phenom 9550 (CPU)

Thanks already,
Yannick.

PS: Don't mind the product, I just selected something, game wasn't in the list