Is my power jinxed?

I run my 250 watt switching amp with a PS Audio Duet on a dedicated 20 amp line. The Duet has been kicking in and out lately, not so much late at night. I tried another Duet and a Quintet with the same results. There is no problem running the amp straight from the wall. I tried the Duet in a secondary system with the same results. My front end runs with a Premier on another dedicated 20 amp line with no problems. I have a whole house surge protector at the main panel. I had a smaller 125 watt amp until July, but the problem just started in the last six weeks or so.