[mamasboy]

found this on the web:

You may have to perform the following sequence if your vehicle's battery has gone flat or it is disconnected.


If your key fob has just stopped working try this:

1. Unlock your vehicle with the key in the drivers door lock, do not open the door.
2. Press the right hand button lock button (the button with the padlock symbol or the dimpled button) on the key fob 4 to 8 times.

If the above fails try this:

1. Open the key fob
2. Remove the battery
3. Press any button 10 ten times, and the same with the other button
4. Refit the battery or a new battery
5. Unlock the vehicle with the key in the drivers door lock, do not open the door
6. Press the right hand button lock button (the button with the padlock symbol or the dimpled button) on the key fob 4 to 8 times