Win 7, Outlook 2007. Have two MSN.com accounts, both outlook.live.com upgrades.
No problems until yesterday. Now Outlook 2007 doesn't get past "Enter your user name and password for the following server" pop-up request for one of the accounts. That pop up just keeps repeating regardless of the password entered. Outlook gets no further than repeatedly popping up that request. The correct password is entered into password field, which is confirmed by successfully logging in at outlook.live.com using that password in a web browser.
https://account.live.com/activity also indicates that the login attempt was a "successful sync."
The password request popup keeps repeating even though the "Remember password" box is checked.
The other account downloads and sends email with automatic signin to account (there is no pop up request to enter user name and password).
Have already tried:
Creating a new profile having the account with the problem.
Problem occurs after starting Outlook in safe mode.
Norton add-in (COMS) was already disabled.
Resolution steps at https://support.microsoft.com/en-us/kb/290684.