I don't seem to recall having this problem previously. It seems to be a new issue.
For what it's worth, I've authorized and deauthorized several times before, as I'm a librarian getting screenshots of the process for the handouts I create for our patrons. But suddenly, today, it just won't let me do it.
Can you please let us know your OS configuration?
Well...I don't know quite how much info you want, so I'll start with the basics:
15-inch 2009 MacBook Pro
OS X 10.9.1 (13B42)
Here's more information. It works like a charm in a different account on my laptop, but not in my main one. Some file or files must've gone bad in that account.
Is there a way to just uninstall, and then start totally from scratch?