It sounds quite possibly like a General Module problem. Many basic electrical functions of your X are controlled through this module (Door locks, interior lighting etc). Check and make sure all fuses are good first off. If you have power everywhere then you'll probably have to have the module diagnosed via GT1. It may just need to be re-coded as I've had to do this to mine for no apparent reason.

A reputable indy shop with the software could probably do this for you. I would go the dealer route if no one else has the GT1.

-Ben