if you are talking about the sticky curser in the first screen whan AH loads (which I have), then just alt-tab out of AH and alt-tab back in again and it frees up the mouse.
I have the problem (had it 1-6, went away with 7, back with8) and that works for me. A lot quicker than creeping you way to video settings which I first did. Some one said
press H, like in game, but that didnt work for me. AH works fine for me BTW.