Well, I also reported a momentary BLAST at full volume not long ago, but my car is an 06/08 build. And it happened just 5 minutes after leaving home, and at moderate volume.
In my case I lowered the volume in the steering wheel right after hitting 'CD' (from 'SAT') on iDrive. As I was doing that, BOOM! It's obviously a software issue more than equipment malfunction, but I want that resolved. Hasn't happened again, but don't use the car much. I'll wait until my next 'low mileage' oil change in 10 months to try to get the software downloaded (hopefully improved). Glad to learn there's a second person who experienced the same BOOM!