yesterday, the weather was great and I had the windows down as I drove up to the post office to drop off a letter. When I tried to open the door, it wouldn't work?! I had to close the windows before it would let me open the door! Is this a design feature or another Mini glitch?

 

Sounds like a problem with the door latch mechanism. The door should always open regardless of the fact that the window is up or down.

 

Glitch or unrelated coincidence

 

don't want to sound patronising but did you try to open it twice, as the first attempt would only unlock that particular door, if you had gone faster than 10mph up to the post office. this is the anti car jack device.