Check fuses A5 and C3, but I bet they're OK because you don't report issues with the windows or instrument lights.
So, I suspect that the overhead interior light and integral switch is your issue - the switch is either dirty, or one of the contacts broke. Disassemble by prying off the IR sensor covers to locate the screw underneath, remove and visually check for proper operation. If that doesn't get it, report back.
The next thing to check would be the door lock modules in each door and finally there is an alarm system tie-in to this circuit as well.
