I was having the same problem, and after trying several things, I finally decided to just leave the screen running and went away for a while. Of course I was logged out for inactivity, but when I logged in and resumed my character, I found that I was able to continue with no further problems. I don't know if what I did was the reason it works now, but Its worth a try for others experiencing this problem.
Confirmed that this worked for me, click on options and check the Safe Mode box. I was having the same problem and now everything works.