One problem related to wiper has been reported for the 2007 BMW Z4. The most recently reported issues are listed below.
Low battery situation over the winter caused the vehicle to slip into "transport mode" where the ac, defroster, and fan speed will not work. This creates a hazardous visibility situation due to the defroster not working. As I understand it, the transport mode is supposed to be disabled when the car is delivered to the us but some dealers mistakenly turn it off rather than disable it. To disable it you must return it to the dealer and pay for a high service visit for a few moments of programming.