Like many others I was having a problem with the screensaver not starting, and the monitors not powering down (had the same problem in Vista)
After going through a series of tests using msconfig and getting no results, I started to un-hook hardware. The first thing I un-plugged was my Contour Shuttle Pro v2 NLE editing controller.
The screensavre started right away and the monitors will now power down.
No solution for the moment except to keep it un-plugged from the USB port until I need to use it.
My hardware:Asus P5E-VM-HDMI mobo, core duo E6750 2.66GHz, 4GB RAM, Nvida geForce 9500 GT and 2x Dell 2209WA monitors.
A trouble report was sent to Contour, and I hope they will respond positivly.
I hope this helps someone else.