monitor losing sync

All,

I just bought a new system with a ATI (Sapphire) Radeon X800 XL 256 MB
running Windows XP sp2. Everything is good except for one problem.
When I am logged in as one user then switch users and then logout the
second user my monitor loses sync. Even if I turn my monitor off and
then back on I get no signal. I have the latest Catalyst drivers
(5.7). Any ideas? Does this sounds like a problem with the video
card, my monitor, software/drivers? Any idea how to troubleshoot this?

Any suggestions much appreciated!