I had a load of errors from Messenger when I installed something from Windows update. I uninstalled them and it was fine after that.
I think you should go to add/remove programs (via control panel) and see if messenger has a 'repair' option when you click on change/remove (I'm not sure if it will say that...I'm at college at the moment so I don't know!)
See if it sorts itself out when you click on repair. Hope this helps :)