Brian, thanks for your reply. To answer your question: no I do not have any couplers or repeaters.
I read the troubleshooting link you posted. In order to evaluate whether a coupler might be useful, I tried performing x-10 commands with the dryer on. At first it seemed like it made a difference (x-10 commands were received) and then it didn't...almost seemed intermittent. Sometimes it appears that only x-10 on messages are being received while x-10 off messages are being ignored. And then they are sometimes both ignored.
Indeed this sounds like there is some type of power line noise that causing issues. I can't think of anything that has changed electronically (new appliances, electronics, etc.) and I don't have any CFLs. But obviously something is causing a problem...could it be a neighbor's house?
Anyhow, back to possible solutions...
If having the drying on doesn't solve the problem, is a coupler then NOT the answer? Is a repeater the way to go then? I need to find a relatively inexpensive solution (not involving an electrician).
Some more background...I have a two story 2800 square foot house, no basement. My x-10 items are limited to 8 lights and a universal module that I am only using for its built in audio alert.
Thanks,
Kelly