One of the first things that I learnt when I started getting into IT was to read and understand all the blah blah blah. You can't troubleshoot something unless you translate that blah blah blah in to something understandable.
Try going to the event viewer and see if there are any events there that might give you a clue. Then go to the Microsoft web site and look for the Events and Errors Message Center (I'll let you find that one on your own (For some reason Microsoft like to hide this as deeply as possible in their web site)).
See if you can find the event and Microsofts solution for it.
