SRS Seat Belt Light

Hi,

I have a W203 - 2003 C200 Kompressor. 

After some heavy rain my SRS Light came on. This is followed by a Restraint System Service.

If I unlatch my Seatbelt the Buzzer Stops and the SRS Light goes off but the Seat Belt Light remains. If I latch the Seat Belt the Seat Belt Light goes off and often the Buzzer does not sound but the SRS Message appears.

Does anyone have any clues.?

Thanks