Help, Strange Static Sound Recurring

I am a newbie. I have a nice hand-me-down system (from my Dad), a Jeff Rowland Model 1 Amp, an Audio Research LS3 preamp, Thiel 3.6 speakers, and if it matters, a Theta Data Basic with a Theta DS Pro Basic III.

When I set it up, it was fine. After a few weeks, I awoke to hear loud white noise (static) coming from one channel. I had left the system powered up, but the amp was off and the static persisted. I could not turn the amp on. When I would push the power button, it would light up, but would not "catch" and stayed unlit.

I called Rowland, and sent the unit in to them. It checked out perfectly. I hooked it up again and it was fine, only to repeat the problem. The Rowland people were flummoxed. They had played it continuously for a long time with no problem. I sent it off again, but no problem found.

I talked with a local (Minneapolis) audio guy who speculated that it could be that the power coming into my house is weak or inconsistent. I then tried a computer UPS (uninterruptible power source), and I thought the problem was solved, but alas it recurred.

Someone at one point mentioned that perhaps the 3.6's were a bit much for the amp, but he wasn't saying that was the cause.

At times I have unhooked the speaker cords, swapped channels, changed fuses, etc. Sometimes, unhooking and then reconnecting the speakers seems to make it work, but then after a few weeks, here comes the static again.

Anyway, it is frustrating and the wife wants me to sell the whole system. I just bluebooked it at 5K. I might do so, but I'd love to solve the problem.

Any thoughts? Anybody wanna buy it?