I have not read of anyone on the various forums in the U.S. having this type of problem with their 335D. Bear in mind that the population of 335D's is much smaller in the U.S. than over there, so there is a lower population of cars as a result. So, fewer 'opportunities' for someone to experience your problem.
How old is your car? How many miles? If your local garage cannot access the ECU, you might be well advised to get your car to a BMW dealer, so they can properly access the ECU and (hopefully) determine what is happening. Please keep us updated on your progress, as your experience might be valuable knowledge for D drivers over here. Good luck!