I have the same problem. Left the kids at school the other day and same afternoon it suddenly stopped working without any reason (no accident/maintenance or adjustment to anything on the car).
Granadaman, jho and if anyone else have the same problem, have you solved is?
I am charging the battery now and will drive a longer distance some day soon but I assume it won't solve it. I have run out of batteries several times but never had this problem before.
If I come to a solution I will post it here.