Some users have recently had their accounts hijacked. It seems that the now defunct EVGA forums might have compromised your password there and seems many are using the same PW here. We would suggest you UPDATE YOUR PASSWORD and TURN ON 2FA for your account here to further secure it. None of the compromised accounts had 2FA turned on.
Once you have enabled 2FA, your account will be updated soon to show a badge, letting other members know that you use 2FA to protect your account. This should be beneficial for everyone that uses FSFT.
I own a Sapphire HD 7970 6GB Vapor-X Toxic Edition and I am experiencing the same problems exactly.
Especially while gaming (Planetside 2, SWTOR, AC3 etc) and after an hour or two (it seems random) the computer locks up completely, no BSODs, temperatures are fine, GPU usage is normal for those...