I'm happily mining using 11.11 x 2.5 combo. Got nothing bad to say about it.
I suggest you start messing around with vector width settings (vectors 1, 2, or 4) and work sizes (64, 128, or 256).
vectors 2, worksize 128 is a very universal combination.
A couple of my 6770 cards are doing great at vectors 2, worksize 256 while some other oddball mix of cards prefer vectors 2, worksize 64.
Do some benchmarking and fine tuning, you'll get your performance back.
Whichever settings you test, make sure to let cgminer run at least for an hour before writing down the results as conclusive.
EDIT:: P4, are you a couple of miners down or did you point them away from bitminter? Some new pool being tested?
Thanks a bunch I'm actually in the process of trying to sell it. I'm at 309Mhash