i seem to have a weird problem with my learning remote. it is a learning remote that came with my THX preamp.

Control for my tv, dvd, laserdisc vcr, etc is fine, but now it won't work for my cable box. but if i get closer (about 3ft) to be cable box the remote then works the cable box.I have never had this problem before and have been using the remote fine for years.

Does anybody have any guesses to what is going on and how i can fix this? thanks