Has the motherboard been recapped? I would bet that if it hasnt that would cause any number of issues. Before I put a 520 board in the one I sent to uniserver (kept that board) it bricked a hard drive. I was able to reformat it using another CC and its usable again but the boards send strange info once they start shorting. The desktop file may be jacked. That always used to happen on my 638CD, and if the board is jacking up signal to the drive that can happen pretty easy.

Good Luck.