I've experienced the same a few months ago. Problem is on the key control card (with a greater possibility at the switch *under the button*) Control card is the small green card when you see replacing the battery of the key. If you can't replace it by yourself find some where who repairs radios or TVs. They can easily change the switch or find the possible other problem on the card. Small accessories (like alarms xenon kits etc) shops also can repair it.
Regards,
Utku.
Utku YARAN, February 2012