What settings are you using exactly for cgminer?
Seems like you're pushing your GPu too much.
You could also try using Linux.
Right now, the settings are just what I showed. It's just the mining pool, username, password, intensity=12.
On my other machine, all four of these cards can run overclocked and with I=20 with a few rejections but no hardware errors or crashes. So I would think the I=12 with no overclocking should be well within their capabilities. I have tried bringing it all the way down to 8 with no change in the result.
I spent 2 days trying to get this same hardware running with Ubuntu, but was having issues with cgminer crashing there too. I went to Windows because I had already gotten one Win7 machine mining stably, and mistakenly thought that if I used the same video cards, drivers and OS, I could expect similar results.