[Al Skierkiewicz]

Phil,
Interesting problem...You say you don't have any problems at work just at your house.?! Could be that the ground and neutral are reversed in your house wiring. Easy to check with a simple power checker you can get from Home Depot.
You may have an open neutral. Are you burning out more light bulbs then you think you should? Have you scoped the power supply line on your board? Does it have any ripple or RF running on top of it?
If you see a lot of RF on the power supply (fuzz on the DC on a scope) it is possible you have something in the house that is radiating. Common sources are touch on/off lamps, wireless phones, and believe it or not, aquarium heaters. Another source is X10 lamp controls which use the power line as a bidirectional serial line. They are only designed to transmit during commands but you might have one stuck in transmit. Are your neighbors close? They may have something as well. Finally, a souce of interference you would never think of is your TV. Do you have a plasma display which is a real source of noise. Other TVs also produce power line noise as well as computers. If you suspect one of these, unplug it from the wall to make sure it is not the culprit.
Al