I read up a little on the XTBM, and it sounds like a good place to start. With the x10 factory issues lately, I doubt if I will be able to get one. Any suggestions on where to buy it? I see the ESM-1 and testerlinc are discontinued.
You're in luck!
Thankfully, the XTBM in not made by X10, but by our very own Jeff Volp. You can find the ordering information on his website:
http://www.jvde.us .
It wasn't clear (or I missed it), but can you control the outlet on the TM751 itself from the remote? If not, then perhaps the RF receiver is fried.
another thing to try, for testing, is to rotate the code wheels of both the TM751 and the remote all the way around. Sometimes the contacts get dirty, and they don't work as well.
You might also try another housecode, just for kicks.
If the remote CAN reliably control the TM751, and it sounded like you could intermittently control things, then I'd look for noise, as well.
One thing people sometimes overlook (it happened twice to me), is CFL bulbs. They can work fine for years, and then suddenly start failing. They still light up just fine, but they start to throw out a ton of noise, and can take down the rest of your X10 system (in one case, my NEIGHBOR'S failing CFL bulb took down my entire system!).