Same happens to me with PP2010 during long renders. Screen comes back briefly if I move the mouse. Once the render is complete the screen stays on okay. I'm guessing the monitors aren't getting any signals and so go into sleep mode when the CPU is busy. CPU is a i7-860 quad core.
You could look at your power settings in the control panel.

Also Windows 7 Ultimate 64 bit, but using two 5000 series graphic cards running 3 Samsung monitors.