First, turn off the hacks! Just kidding Winters...lol
I would check under services to see if both the PnkBstrA.exe and PnkBstrB.exe are there and running. This is not a cure all but usually the case.
If that doesn't help delete the BF3 Punkbuster folder in appdata then re-install. The appdata/local/punkbuster/bf3 is a hidden folder so you will have to make it view-able.
Update your graphics driver if the above fails.
Finally, re-install the game as a last resort.