Hello, I just bought H2V and multilayer works fine 150-223fps but in sp the frames are only around 3-8fps making it unplayable my specs are:

Athlon 4000+ X2 2.01ghz
1GB of ram
BFG 7950GT
ASUS M2N SLI DELUXE (motherboard)
Windows Vista Ultimate

Also if I pause the game for about 2-3 minutes it becomes fully playable.