We are going to try to restore the webserver files from 24 hours ago, before the change was made that caused the problem.  The sql database is going to stay the same.  not sure it'll fix it, but we will see.

UPDATE:  WE DECIDED TO HOLD OFF.  WE ARE HOLDING OFF RESTORING ANYTHING UNTIL WE GET MORE INformATION.

We are thinking there should be a way around this problem -- a change to the database or a tempNorary code change to allow admin login access.  HELP!

Noticed this from Mitch Sellers.  This is a close relative to the problem:

http://www.mitchelsellers.com/Blogs/tabid/54/articleType/ArticleView/articleId/125/Default.aspx

mitch's fix did help.  we deleted the new row that I had marked as required and after a few minutes (not immediately after deleting the row), logins started working and I was able to go in change it so that profiles were no longer required for registration or login.  whew. lived and learned.  Thanks, mitch, john!

Just a question on product design:  I understand this is something I should have tested outside of production and I was a "bad user" for accidentally adding a field to the profile improperly (and others have been "bad" but requiring a field but not making it visible) but should that really cause a "critical error" that prevents any and everyone from logging in?  At least consider maybe checking the visible field when required is checked?  Doing some kind of check/alert at profile change time indicating "hey, this change you made is going cause all logins or registrations to fail...do you want continue?")