Well, that was helpful! I used the online chat help. The tech took control of my machine, poked and prodded for a while, and seems to have resolved the issue. What worked?
1. First, she downloaded and updated the Adobe Application Manager.
2.This allowed her to successfully launch Premiere and deauthorize the computer.
3. She quit Premiere
4. Then, she renamed user/library/Application Support/Adobe/Premiere Pro/6.0 to 6.0(old)
5. She relaunched Premiere
6. We reauthorized the computer
7. It worked