Admin login is constant loop with no error messages after upgrade.

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I just upgraded from version 5.4.1.1. to 5.4.2.2 following these instructions:

http://www.concrete5.org/documentation/installation/upgrading_concr...

There were no error messages, but can no longer login to the site, as the login page presents a constant loop with no error messages. Even when I reset the password, the problem persists. Can anyone help - please.. ???