Picked up a new G5 powermac Thur evening. Set it Fri AM and on three occasions there loud pops coming from the machine. After the last it was dead. Took back to Apple store and they think power supply blew and replaced unit. Set up new unit today and another loud pop. Unplug and get an outlet tester and find the outlet does not have an active ground. Change to good outlet and run off of an APC uninteruptable power supply that I was using for my PC box. Just ran the Apple extended hardware test and it passed. Am I OK? Are macs that sensitive to non-grounded outlets? Thanks for your help.