I'm hoping there is an M6500 expert out there who can help me...

I have a Precision M6500 notebook, late 2009 with a quad-core i7 and Quadro FX2800M graphics. Recently, it has developed an issue where, without warning, the screen will blank and the system will enter a catatonic state. I think it is not hung as I can see random flashing from the hard drive light, but it will not respond to any attempt at a blind shutdown either by keyboard command or by pressing the power button (Windows set to shut down on power button press). I have some reason to believe that it is not even seeing the keyboard since a press of the CAPS LOCK key is not reflected in the system LEDs. Ultimately my only option is to force a power down via a long press of the power button.

Other observations:
1) I don't think it is a software issue as the problem persisted even after a wipe and reload of the OS.
2) I don't think it is directly related to heat and/or system load. I can run the system for hours under heavy load with no issues. In fact, the problem usually seems to occur under minimal load (i.e., web browsing), in some cases shortly after waking from sleep.
3) The timing seems to be completely random. I can run the system for over 24 hours with no issues, but then get three incidents in a day.
4) The screen blanking is not just an inverter/backlight issue. There is no sign of anything on the screen when it occurs.

Does this sound familiar to anyone? I really need some help here...

Thanks...