First time Mac-owner here (though I've used them quite a bit). I just bought a used Quicksilver 733 G4 that seems to be having a weird problem. It powers up and runs fine with VGA, but plugging anything at all into the ADC port (whether a studio display or a Belkin DVI adapter) seems to kill the power. Nothing will turn on at all as long as something's plugged into the ADC port, but as soon as you pull the cable out, it works great. Any thoughts, ideas, help? Thanks!