I recently had a situation where my laptop (a macbook pro on Mountain Lion) stopped connecting to BBB over the USB (virtual ethernet). I thought that it was a configuration issue on the BBB, but I copied a factory image from the eMMC of a new BBB to the one I was trying to get to work. Long story short, I discovered that both the new BBB and my BBB could no longer communicate with my macbook pro over USB. I’m still trying to figure out what changed on the laptop, but in any case that may give you a place to start looking.
Duane