There are some items you can check first:
Drivers (reinstalling, try old versions(gigabyte site)you'll have tried this a few times by now i guess:( ... )
Temps, OC GURU ll
You have a good quality PSU 600W+
Remove any other peripherals, including stuff plugged into the M/B thats not needed to run
Memory test, lots of freeware to help
Bit harder:
Default/re-setup your M/B, read the manual
OS reinstall if possible, spare HDD plus demo windows can help ease the pain here, but rules out anything else installed
Then you should contact your retailer and keep your fingers crossed.
good luck