This rings a bell...MIDI Life Crisis wrote: The WiFi on this Mac Pro has never worked correctly and only rarely can I connect to my AT&T Uverse router, so I usually leave WiFi turned off. I tried a new router (or course it wouldn't even connect to the AT&T modem effectively) and had turned on WiFi on the mac, but forgot to turn it off. I noticed that it was on and as soon as I toggled it off, the MTP2 came back to life and is now as sprightly as the day it was born.
Hope that is helpful to others.
Could the order of the Services/Connections in Preferences>Network have something to do with this?
Have you tried creating a new BT or WiFi connection?