RDP causes a reboot on remote when trying to copy

Hi all,
I am RDPing from my laptop (VISTA) to my desktop (WIN XP PRO SP3).
When I attempt to copy from the desktop to the laptop, the desktop
locks up and does a reboot? I can do everything else when connected.
Surf the net, check my email, do my studies with quizes etc.. with no
other problems, just the coping problem.
If anyone has any ideas I am listening. I did read about Teamviewer,
but I would like to keep with the RPT if possible.

Thanks for the help
Texasowl (Still going in circles)