I've got a similar rcl problem... when I bought the car I got one red key and two blue ones, one blue key had always worked fine and the other has never worked. It's the correct key as it opens the door 'manully' just not with the remote. I've tried replacing the batteries and the re-couple proceedure outlined in the manual but still no joy, the red light flashes when I press the button and everything, just no unlocking. Any ideas?? P reg Brava 1.6 ELX btw.
BTW - if it's of any help the re-couple proceedure as stated in the manual was (as best i can remember it):
1. Make sure alarm switch is set to on (by the fuse box)
2. Leave key out the ignition
3. With car unlocked and alarm off press the little button by ur interior light and alarm led with a pen and keep it pressed, led nearby should start flashing
4. Put keyfob next to little button thing and press the unlock button
5. Led should stop flashing then go constant to indicate coupling has worked.
Job done, didnt work for me but might for you, hope so.