Just for the record, I used a backed up copy of the database to replace the database I had hosed up with the duplicate control ID.  I lost a little work, but much less than the likely damage I would have caused mucking up the database. 

I know this may be nothing more than an idiot-proofing idea, but it would be great if DNN could warn the admin if a duplicate control is being created.  I had no idea untill I had already logged out and tried to log back in, and by then it was too late.  I can tell you that it will never happen to me again, but others may fall into this same trap.  Considering that it totally locked me out of the site, it could be a very big deal for some portals.  I'm glad I don't have any actual users yet, and that I had access to a recent backup.  This could have been a total nightmare otherwise.