do you have a second remote? if so, and it works, we can narrow the problem down to the first key.
how about interference from a local radio transmitter? i had this problem at a friends house. no problems anywhere else. do your problems have any pattern to them depending on where you're parked?
i'm not too sure that the key charges when the car isn't running.
could the contacts on the key be dirty? some electrical contact cleaner might solve the problem.
those are just a few ideas.