I'm using the RF20 and MRF100b with a SA 4250HDC cable box. When I first set it up, it seemed to work flawlessly. Now, 3 days later, it works only sometimes. If I try to type in a channel such as 1329, I'm lucky to get to 132 before it tries to change the channel. I push Guide and sometimes the guide comes up and other times it doesn't.

If I change to the MRF-260 and a narrow band MX remote, will this solve this problem?

Thanks!

Switching to a MRF-260 and a narrow band remote will definetly improve your situation, or you could just try to relocate your existing RF base somewhere with less interference. You could also try (if you have'nt already) moving the emitter on the front of the cable box, as the flash can sometimes be too strong for the box. If you do decide to upgrade i would recommend spending the extra money for the MRF-350, this way you have the added benifit of the extendable antenna, plus the 2 extra IR outputs all of which have variable control.