Check your conf.ini file. If you run a dx10 or dx11 card, make sure this line has 1 at the end:
Render=D3D10_1
Hmm, are you really sure about this Jaws? Maybe it works on ATI cards but when I set it to "Render=D3D10_1" instead of "Render=D3D10_0" which is the "official" setting for DX10 my game runs in DirectX 9 instead of 10 (on my Nvidia GTX 580 card - checking which render is running via the LCD applet for Fraps). I guess that option is not valid (at least not for Nvidia) and the game then defaults to the lowest default setting beeing Dx9?
My average FPS on maximum "very high" settings while starting the Hurricane mission over Dover is around 35 with Render=D3D10_1 (resulting in Dx9) and around 75 with the Render=D3D10_0 (resulting in Dx10). I also get visual artifacts in Dx9 and it looks worse (naturally).