99 Regal Remote Entry Failure

Our 99 Regal LSE has developed the same remote entry system failure that I have seen posted here. Found the reprogramming procedures and tried them all without success. I have also checked the relevant fuse and all look ok. One thing that did work....with the key in the ignition and in the on position, the key fob lock/unlock did work if only intermittently.
Next step is the expensive dealer visit. Any ideas on the cause and fix before I give in?

Thanks in advance.

Have you replaced the transmitter battery?