Theo, have you double checked the serial number ??? I could try the first 6 numbers for you but I don't think that would work.
It may be that the radio has been re-coded at some time and if so the only answer would be to have it re-coded again.
The code generated by using the first 6 numbers, ie. M352181 is 4545 but I really can't see this being correct.
Get back to me after you've checked the serial number again. Good luck !!!
Bigh
November 2009