^ batteries dying or you are not aiming it at the TV/radio/etc sensor properly

 

battery is full, so what should i point at to change the channel? the cable box right???

 

Possibly the battery but I sit 15 feet from my TV/HT and never have to point my 880 at the TV/HT...even when my battery indicator is down to one bar. I can even point the remote in the opposite direction from that distance.
These Logitechs transmit a pretty strong signal.

 

I sit closer than that but like Paul, I don't even point it at the system and it works well.

 

^+1
Direction isn't an issue with the Harmony.

What you describe is what happens to ours when the battery is getting low.
If you have fresh ones in then the unit may be bad.