wow then you have a problem. a quad core and a 460 should max out BC2 and stay above 30fps no problem. after all the 460 is no slouch.
maybe you need to oc the cpu to get a little more out of the gpu but it does sound like you have an issue sumwhere, probably your hdd or mem.
I'm replying to you, but I do not mean to hijack this thread either. It was my RAM. My older RAM went back last week, and I put in new, and better RAM today and the game runs like a champ. 50-80 FPS on high settings.