Comp sleeps & Need a mouse click to wake

Hello,

I have an annoying problem. About two weeks ago, my computer started "hanging up" while I was working it. An extra mouse click brings the computer out of its sleep. This can happen several times in a minute and if I stay fairly active with the mouse, the problem is not observed. But if I work more slowly, this becomes annoying as I have to "click" my mouse to resurrect the computer from its idle.

I have a logitech cordless plus optical mouse and the receiver plugs into a USB port. I presume the mouse and USB port are fine, and I presume something is awry with my system software. This my hypothesis only.

Any suggestions as to how I can diagnose and solve the problmem?

Scott