I have the same system as you, but running win7 64-bit, with the same freeze issue. In my case, the freezes were occurring about every 2-5 days, sometimes multiple times in a day depending on the video driver I was running (phase of moon, temp, etc...). After sending in for RMA, ASRock replaced the motherboard and sent it back to me. Since I got it back on 12/23/2012, I have frozen it 3 or 4 times and had another RMA issued, but have not sent it back in yet.
I noticed they just posted a 12.11 beta driver on the ASRock website. I may give that one a try.
Any progress on your end ?