Alienware m17x - Screen goes black when idle... help!!!

I have an Alienware m17x R2. It all began when the laptop would not go into hibernate mode, which it did without any problems up to about 6 months ago. When I hibernate, the screen shuts off, but the lights on the laptop remain on as well as the fans. Dell replaced most of the major components - GPUs (dual ATI Radeon 5800 series), dual hard drives, fans, and motherboard. I've also re-installed all the system software. After ALL that, the problem still persisted and I just learned to live with it by shutting down the computer each time.

Now, the laptop will go to a black screen when idle for about 10 minutes and there is nothing I can do except a hard reset. Is there any help out there? Your help would be greatly appreciated... thanks so much!