See if you have power management activated on your system. Sounds like the power management is shutting off your monitor and then isn't able to turn it back on when you move your mouse (do are moving your mouse, right?)
Shut off the power management and see if that helps.
How happy is the blameless Vestal's lot!
The world forgetting, by the world forgot
Eternal sunshine of the spotless mind!
Each pray'r accepted, and each wish resign'd.