I have a leased 2009 535xi wagon that is now in the shop for this same issue. blew out 1/2 the elctronic equiptment.
Worse, Last year I had to return a 2008 525xi wagon that the entire wireframe had to be replaced and the car never worked properly again... it was in the shop over 50 days and I was forced to use the California lemon law to exit the lease.
Both instances happend after heavy rain. The first - my car just stopped running. dead, had to be towed away. The second - warning signals started malfunctioning, then the headlights, alarm and entry chimes...
This last instance they tried to claim the electronic failure on my dogs dripping in the back. crazy. it's a station wagon isnt it ?
it seems like i should have moved into a different car, as this wagon has some issues. sad because I love the car.