Hi, I have this too. It happens about after I played for 30 minutes. This is the only game which cause this. Tried RO2, ARMA2, cod: black ops and other games. All temps are okay. Tried system restore but it didn’t work. I also tried clean install the amd drivers.
Windows 7 64bit SP1
AMD Phenom II x4 B55 3,2ghz
AMD HD6950 1GB with 12.8 drivers
Creative x-fi extreme music card
16gb corsair 1600mhz ddr3
Here is the chivalry launch backup file