Have you tried lowering your memory clock speeds or core clock speeds? I had a similar issue with one of my gigabyte 7950's and I had to lower the clock speeds unit it stopped doing it. I know it's not as fast but at least I have non stop mining going on. If it happens again even after you made your changes on the hardware side try running it at default clock settings to see what happens.

Also I switch to GUIminer -scrypt version and I am getting the same results as directly with cgminer but it seems more stable. GUIminer also has a auto start feature that I like.