Reminds me of the story of the serviceman who got a call from an old lady who said that whenever she flushed the toilet the doorbell rang.
Thinking she was a brick short of a load, the serviceman checked it out, only to find the doorbell wiring in the attic was run across some water pipes, and had rubbed a bare spot in the cable. Whenever the toilet was flushed, the pipes vibrated enough to cause the wires to touch together, thus the ding-dong!
Check for a short in the attic.
Rick Miell