Okay, for some reason this is what happened. CAProvider wasn't working. What I was seeing is perhaps Apple's halfhearted MIDI java implementation. It is apparently truly half-hearted considering it was eating half of the upload message, even when it was a new burned PIC which was sending lots and lots of requests.
So, anyway, I installed plumstone (rebooted) and not even that worked, so I installed MMJ and now suddenly I have two versions of my UNO appearing in MIOS studio. I hooked up the new one in the routing and it uploaded.
:-\