its been frozen at about 35% for the last 5 hours... I thought it might have been just downloading but now Im pretty sure it is stuck. It did this with the MoP beta as well. I never even bothered fixing that just said screw it.
Look through the first few pages in the forums - lots of people are having this problem, and there are a number of things you can try to see what might resolve it. There are other threads where lots of people have been discussing it.