原帖由： adlerpe ,
Is the iMac plugged into an outlet with good grounding, or is it plugged into a 2-prong outlet with an adapter? If the computer doesn't have a good connection to ground, static electricity can build up in the system to the point where the monitor stops syncing correctly. The fact that unplugging the computer for 24 hours eliminates the symptom for awhile supports that idea; letting the computer sit unpowered gives the capacitors time to bleed off the stored static charge. If the iMac is plugged into a grounded power strip or surge protector, check to confirm that the power strip has a solid ground connection at the wall outlet. Get a ground checker at Radio Shack or a hardware store, and confirm that your iMac is plugged into a true grounded outlet. You can also take your iMac to a location with a confirmed grounded outlet, plug it in and see if the problem recurs.