Hi,
You might be interested in reading on our Thoracic outlet syndrome forum.
TOS for short, it has some of the same symptoms you mention.. and is not a well known condition, so is often missed or mis-dxed.

more info here-
http://neurotalk.psychcentral.com/thread84.html

Is the tingling/buzzing actually in that muscle or could it be the muscles under that one?
the rhomboids are located under that muscle in the same area.

My rhomboids will get sore and weak if I allow my shoulders to roll forward for too much time.
Basically they can get overstretched pretty easily.