I successfully used the AccountManagerPlugin with version 0.10.3.1 of Trac + MySQL. After the release of Trac 0.10.4 I updated my Trac installation to fix some issues related to MySQL.
After upgrading to 0.10.4, AccountManagerPlugin does not seem to work correctly anymore: Whenever I visit one of my Trac projects and login, my session expires after a short time, sometimes directly after login. The logfile did not prevennt any useful messages, although I set the log level to DEBUG.
This issue forced me to downgrade to 0.10.3.1 again (I had made a Backup of course).