UPDATE: GotDotNet Workspaces Troubles Solved, RTFM anyone?
The stunning Betsy Aoki, the Community Program Manager for MSDN and TechNet emailed me earlier with details on my recent GotDotNet troubles. (Reminder, I met Betsy at a recent Nerd Dinner. She found me to be dapper, and preceded to be cyber-stalked by one Phil Weber ;) )
Betsy has kindly pointed out that most of the GDN problems are caused by what she calls "unclean Passport cookies." I'm unclear on why I'm unclean, but a clear of the browser cookies and cache and a little mercurachrome cleared the whole thing right up.
She has also seen fit to update the GotDotNet FAQ with all the details on how to fix troubles you may have.
Turns out that not all that fails to glitter fails on the server-side, if I may mix my metaphors. The new GDN FAQ has good information that solved my problem; do spread the word to people in need of assistance.