I'm encountering this problem in Windows XP - (no screensaver, or timer monitor shutdown).
The only thing I can find is people dealing with wireless mice/keyboards and a microsoft fix, but I'm using the standard keyboard and mouse on my MBP.
Maybe it is something with HID compliant devices, because they are listed in my hardware devices, but maybe that's something internal because it is an MBP vs. external.
Anyone ever solve this? I installed Windows XP Pro with Bootcamp 1.2 - and am mostly pleased - this is my only real problem.