I bought a RR501 w/ Palmpad(HR12A).
I chose one of the switches on the wall work and control my lights outside. It is set to "C/14". I programmed the transceiver and remote to "C". I switched the remote to "9-16" and the transceiver to "9" setting and have tried every "on" combo in the device and I can't get the lights to come on.
I am stumped.
1. Have you tested that the HR12A can control the RR501? The switch on the RR501 is for the outlet built into the bottom of the RR501. Set it to "1" to control it on Unit Code 1, Set it to "9" to control it on Unit Code 9.
Make sure you can control that outlet before going on (you should hear it click on and off, and something you plug into it should turn on and off).
2. Make sure you are plugging the RR501 into the same outlet where the Maxi-controller worked before?
3. If you manually turn the light on (at the switch), can you turn it OFF with the remote? What kind of bulbs are in the light fixture? (Nearly all of the X10 switches need to be used with Incandescent bulbs. CFL bulbs won't work with them, because the switch can't pass enough current through them when it is off to listen for commands.
4. As Brian suggested, there is probably something else in your home that is causing noise, and the Maxi-controller might not be bad in that case. Try plugging it into a power strip (with nothing else on the strip), along with the RR501, and see if you can control the RR501 with it. If you can't, try moving that strip to different places in the house. If you can get away from the noise, and you find that the Maxi-Controller is able to control the RR501, then you know the Maxi-Controller is still good. If you can't find anywhere at home that works, you can try taking it to a friend's house, or to work, and trying it there (it can't hurt).
5. If it is noise in your house, I'd look first at anything new that you got right around the time the problem started (as Brian suggested). New TV, Computer, cell phone charger, CFL bulbs, etc. If you can't figure that out, there is always the "breaker box test". Turn off one breaker at a time (you may need to move the RR501 to another outlet if you shut off the circuit it is on), and see if the problem goes away. If the problem goes away when a certain breaker is turned off, look at what is on that circuit. You may need to filter a noisemaker.