Thanks for this thread as it's given me a good starting place for my Problem. I have a 318Ti and the boot (trunk) lid won't stay shut. Every time we close it, you hear the automatic release mechanism activate and unlock it again. Only once the car is fully locked will the boot stay properly shut. We are having to drive the car at the moment with the warning light on on the dashboard and witht eh boot lid only shut on it's safety catch.
It certainly seems to be a short circuit as the problem has got increasingly worse over the last couple of weeks.