Could there be a punch-through on the av3100 superseding the taught commands? The x10 remote, after changing to IR, does it get a reaction from the IR543 at all? Any keys? Make sure you have Rf transceiver unplugged, just so you'll know if a light dims, its via IR and not RF.

What is the exact model # of the X10 remote? You might have one of the funky x10 remotes like I have. I have 3 UR19a, payed $1 each off of ebay. The ur19a is a very old remote, but mine has codes for DVd's & tivos and such. Which it shouldn't. And instead of code 014 for IR and 013 for RF. It uses 810-IR, 811-RF. I can't find a matching codelist anywhere. The codes I know about, I had to have them blinked back or wouldn't have known what they were.