Did u check the card temps?
U can try on your friend's computer(make sure he has a good PSU) to make sure whether the games are still freeze or not. If it yes then it's your card is in trouble.
No need 1200W of PSU, u just need a good brands(like Corsair, OCZ, Antec, SilverStone, etc)
Also make sure all of the power connector cables are properly inserted.