While the overall build has been tested by Josh, I think a lot of people have been getting bum bricks. Did you purchase yours directly from Dell, or from a third party? If it was the latter, then you may have received one that did not pass Dell's quality control check, and the third party is just selling them at a cheaper price because they aren't up to snuff. I'm assuming that's how mine is. I could use my brick to game just fine, but I couldn't overclock at all, otherwise it would force the system to power cycle.
Because of that, and my future upgrade choices, I bit the bullet and bought a Eurocom 780. I haven't looked back since...
I'm willing to bet that the issue isn't with the HDPLEX. They seem to be incredibly solid, and it seems like the majority of people are having issues with the Dell bricks.... But, I could be wrong.