hi all, just got a replacement of my sapphire radeon 7870 oc 2gb and i'm still having a few issues. i can play a bunch of my games with no issues, some are more intense than others (witcher 2, etc) but when i play borderlands 2 for around an hour or so it will freeze and go grey with a verticle black lines. i'm using the latest beta drivers (13.6) but wondered if i should try to clear out the old drivers with driver sweeper? any tips are welcome! just want the card to run like normal! oh and i have overclocked to 1200/5700.