Are you running on an AMD, kapersky,AVG, peer to peer? Theya re known issues of conflict with utorrent.
Have you got screensaver and/or hard drive set turn off at specfic time? Any of them kicking in will send utor inot freeze mode.
I hadd same isue with utor, and found my hardrive was configured to go to sleep, soon stooped that and utor worked fine.