I had an issue on my WD recently, and it boiled down to a small capacitor C2 on the driver board that had died and leaked.
It damaged a trace on the driver board between the ribbon cable(from CpU board to driver board) and pin 3 U1 and thus caused lots of probs.
Its worth a look around this area for damage!!! C2 on driver board to the right of Fuse 115