I had a similar problem. my dell precision T3500 would randomly go into a power saving mode and would not come back. I tried everything in the books but nothing worked. finally I updated my dell "BIOS" and bam , my computer started working normally again. try updating your computer bios. go into driver and support , enter your 'service tag' and check for system analysis. download and update your graphic driver and audio driver. hope it helped you - rakesh murthy. pune.