Yesterday brought the problem and today brings the answer. Well, answers. There are two ways you can fix the multiple login issue afflicting your Movable Type install if you placed it in the root directory.

JANKOWSKI SOLUTION

The first is a quick and easy fix that has been termed the JANKOWSKI solution, so named as it refers to the person who posted it on the Movable Type forums.

The Jankowski solution involved modifying your APP.PM file. This is located under the LIB/MT subdirectory of your installation: