Graphics Amplifier intermittently powers off by itself.

I'm having an issue where the AGA will simply power itself off. The fans and lights go off. This will happen in the middle of a game, or while doing something non-cpu/gpu intensive. Windows event viewer typically doesn't show any errors, other than a very occasional dwm.exe error, which seems to be windows attempting to recover. I suspect the AGA cable is to blame, or possibly the power supply. Has anyone had a similar problem? I can't find anywhere on Dell's website to order replacement AGA parts.