Windows Live Messenger 2011/Computer issue

Well we recently downloaded Windows Live Essentials 2011, and I did not want new messenger, but realised that the old one is now unavailable, and now I've gotten used to the new one. Well anyway, it works fine and all, but recently our computer has been restarting a few minutes after shut down. Sometimes you think it isnt going to restart but then it does again about half an hour. Anyway, I have figured out that this problem has something to do with Windows Live Messenger not being closed properly, and it says: ''Waiting for the following program to close: Windows live messenger. Please close the program to resume shutdown''. this appears for about 3 seconds then it just disappears and the machine shuts down. Then it restarts again. This is really annoying as it uses alot of power unnecessarily. Does anyone have any idea how I can fix this? please help.

Thanks, Emma.