[madm5]

I'm a very new M5 owner but i understand that when the service lights malfunction it's usually due to dead rechargeable batteries soldered on the circuit board. They're AA size and any reasonably competent tech can resolder new batteries in place for less than the cost of a replacement board.
As for the doors this will be more difficult tofind cos it only warns you above a certain speed but you'll have to drive along and get a passenger to press hard on the inside of each door to find which one is causing the problem.

 

[madm5]

Do you have any further information on this? I have a problem with my trip meter resetting everytime the car is shut off, might have something to do with this.
-Thanks!

This sounds very like the batteries, i'm no expert but have read in the haynes manual about this, it shows a picture of these batteries soldered on the board, it would literally take 10 mins to remove the old ones and solder in new ones, once the board is removed, any rechargeable aa batteries would work. The board is on the back of the instrument panel