Screen saver issues since cordless mouse installed.

My neighbour is asking for help with this issue: since he installed a MS Optical mouse his screensaver doesn't come on at all. I've checked as well as I can, but not being a Vista user I'm at a loss. He doesn't have either SP1 or 2 installed, which I've instructed him to do, and I wonder if this could be the problem?
Any help very much appreciated.
Thanks.

I would start by trying the old mouse and see it the screen saver comes back on.

Ask him to plug the cordless mouse in, then check windows update and see if there is an optional update for Microsoft HID Non-User Input Data Filter.

If there is, try installing that.

Thanks. :) I'll pass on the information and suggest he become a member on this great site.