I am having the same issue.

Using 5850 radeon HD.
i5 760 at 2.6 ghz quad

Anyways, before today even during p3, and p4, even at release i was not getting this low fps. dipping down to 10 or so. i was using same settings.

Used to be around 40-50 fps.

will try updating my drivers to the "beta" version, since its already latest now.