I also had a few "Dead" GPU states after a couple hours of mining on my 2x 6950 rig... I guess the Intensity 18 is a little on the line for my rig.

I was able to reduce those occurences after increasing my memory clock to 1050 MHz. (stock clock is 1300MHz, I had previously underclocked to reduce temperature).

You might also be interested in downloading this little gem called "CG Watcher". It can control your CGminer entirely and also restart the miner with failsafes such as SICK/DEAD gpus, low kHs threshold, etc.
Haven't used anything this I got my hands on this, also the developer seems friendly and active on his project.