From a previous post:
the key stopped working,
tried the above ,to reset the key, and it worked perfectly, so a huge great thankyou to designer-label for the cure, i thought i might have to take a day off to take the car into the city to the BM dealer,plus the cost, i'm now a very happy bunny.
To reset your key, well for 2004+ versions this works not sure if older ones...
Get in MINI put key in ignition then take it out
Point key at aerial at back of car
press and hold UNLOCK button
press key LOCK button 3 times within 10 seconds WHILE keeping UNLOCK button depressed.
Release UNLOCK button
System should lock and unlock car to indicate programming has been successful.