i just had the same problem today, it turned out to be the overhead panel was defective. acted exactly as you all describe seatbelt blinking continiously and dome lamp not turning off, replace the upper panel and all was fine customer left happy. also the new panel does not come with the sunroof switch or the in car temp sensor they are easilly transfered to the new unit, but does come with bulbs, the part number is 124-820-05-01
Ray
mercedessd@cox.net