Leave it unplugged with no PSU/PRAM battery on it. Those PowerManagers/Firmware chips get so confused sometimes, the only thing you can do is let them drain all the way. You probably crashed the PMU causing stuff not to work. I would do that. It has cured my 9500 board numerous times. Also, make sure the CPU is pushed all the way down into the slot. They will come on, but with no chime if the CPU doesn't seat all the way down. (I would try the CPU thing first rather than letting it sit as the first remedy step)