Computers, especially those behind a UPS, are really bad for X10. I have filters on all my computer equipment, all UPS's, my kitchen fridge, and the washing machine. There are other places that cause noise, but fixing these made the system nearly perfect.
In my case, the computer I filtered (upstairs) does not have a UPS. It is (was) plugged directly into the outlet. Unfathomably, it made no difference if the computer was turned on or not, the module behavior was the same. Like the neighbors, it arrived a year or so ago, about when the problems began.
I have another computer elsewhere in the house (downstairs) that IS behind a UPS, and has no filter. It's been there for years. As far as I can tell it has never caused any X10 noise problems. This machine happens to be on a dedicated line direct to the breaker panel. That may be a factor.
I've had X10 in the house since 1985, and a computer since 1990, and I've never seen X10 behave like this before. I don't entirely understand it, but I know more now than I did two weeks ago. And, I've got more spare parts now than I had before.
Best of all, everything works again.