Even though they are plugged into different outlets they could be on they could be on the same circuit breaker. That said even if they on separate circuit breakers they could be on the same phase. Have you tried a power strip that filters on the computer? It may help.
Thanks. I tried a better power strip (a Belkin Surgemaster) that I had handy. It eliminated the static but there still is popping. I'd be grateful for any recommendations as to what power strip to get.