Keyless Entry Problem on 2003 Honda CR-V

Keyless entry doesn't work all the time. For the majority, the key fob will lock and unlock all doors except the back door on drivers side...Sometimes, it won't lock or unlock...When I get out of the car, try and use the lock button on door, it won't lock any of the doors. I can hear it click, but will not work....Frustrated!

Asked by for the 2003 Honda CR-V
Did you ever find out what was causing this problem?