Remote Desktop & 'Unexpcted Shutdown'

Hi I've been having a big issue with RDP in Vista. I've gone home for
vacation and have been remote desktoping into my PC at school. I've used
remote desktop successfully many times in the past but now I can connect just
fine to my PC but when I log out and try to log back in a few hours later I
won't be able to connect. It appears Vista is crashing or locking up because
I can't ping my machine and any internet applications that were running (IM,
etc.) are disconnected. I have to call a roommate to manually restart my
machine. From one description he described seeing on the monitor a "faint
vista logo", I assumed Vista had locked up and the screensaver was stuck like
that. After restarting I can connect just fine again. This happens
consistently and checking the events on my machine the only thing that stands
out is that there are unexpected shutdown errors before I can't connect.

For example I logged out of my machine at ~12AM and tried to log back in
this morning at ~10AM. In the event viewer there is an error:

"The previous system shutdown at 5:00:55 AM on 3/5/2007 was unexpected."

So something happened at around 5AM that caused it become unresponsive but I
have no idea what. Also, there's nothing special about 5AM, there are such
error events at many different times when I'm not logged in.

After the first time this happened I closed all 3rd party applications so
only Vista itself is running when this happens. This has never happened to me
in common usage nor when I've used RDP for a few minutes to check on
something. I also have no idea why whatever it is that's causing this happens
many hours after I stop using RDP.