Why is the screen saver turning off by itself?

The last few weeks I have noticed the the screen saver on mine and my girlfriends computers are shutting off like something moved the mouse, hit the key etc.. It acts like something that is running the background is shutting it off. There are times when the saver starts but never makes it to the screen and just loads the desktop again. I am not sure, but it may have started around the time I started folding. Could there be a conflict?

We are running Windows XP Pro with the standard screen saver.

Does anybody have any ideas? Can't believe nobody has a suggestion.

It has happened to me a couple of times before but I have no Idea why.I'm not sure if I was folding at that time either.Either way I'm folding now and I havn't got that behavior in a long time.