It says in the documentation:
QuoteWhen you will try to login / logout or manage users from Coppermine, you will be redirected to the corresponding page of your bulletin board. Once the login or logout is performed you won't be redirected automatically to the gallery because your board does not have any function for that. It's up to you to add a link on your board to get you back to the gallery.
Yet, my phpbb site is redirecting back to the gallery. Is this a new feature?
When requesting bridge support - mandatory! (http://forum.coppermine-gallery.net/index.php?topic=24032.0)