What programs are you running whilst you run BF3? Also do you have any FXAA injectors or anything to make BF3 look better installed?
You could try manually updating punkbuster and doing a clean install of your NVidia drivers again. That's what I'd do first anyway.
Did the manual update etc but traced the prob to OC_guru. (worked fine before update but now pb doesn't like it for some reason)..Switched to Afterburner & things running normally again..cheers for the response Suarez7.