Help, my G4 notebook does not start up properly. It doesn't even sound the chime. Sometimes the firmware screen pops up, giving a warning like 'bad memory access'. After a lot of retrying (20 x) the powerbook starts up and works properly. HD, CD drive, memory, screen all seem to be OK once the powerbook is running. I tried a hard reset of the Power Management Unit, which doesn't help. Has anyone been posed with these or similar problems?