I had something very similar happen to me with my '11 Red rear der after I set up new cables. My LBS recommended a 1mm cassette spacer and that solved my issues.

Here's what they used. http://www.universalcycles.com/shopping/product_details.php?id=44100&category=503 (I think it was the 10 Spd Low spacer, IIRC)

Good luck and hope you get it sorted soon!

-efwd

Tried everything except the spacer between the derailleur and the frame. Different cassettes (red, dura ace, ultra, 105), all my wheels,...

It did not work, on some wheels better then others but not as normal. Reinstalled the force derailleur and everything runs smooth...

I guess i'll keep the red derailleur as a spare for my cross or winter bike...