First off: What settings are you running F.E.A.R. on? Be warned that this game is
incredibly hardware demanding if you're using ridiculous settings- yes, even for dual 7800 GTX's.
Secondly, are you using a single GTX or SLI? Going by you're sig, you're only ruinning on one card, but correct me if I'm wrong.
Last off, F.E.A.R. is badly optomised. A lot of people with very different hardware are experiencing poor/strange performance issues. Couple that with dodgy driver support
As a side note, I get around 60 FPS (30 FPS minimum, 120 FPS max) in the built-in benchmark w/ the following settings: 1280*1024, 4xAA, 16xAF, Vsync OFF, Soft Shadows OFF, all other settings maxed out.