$live_site variable of configuration.php

Joomla! tries to automatically detect your web site root URL (ie: http://www.joomace.net) by itself because this information is needed in many operations, especially those dealing with making links and URLs.

Because of a faulty web server setup the detection process sometimes fails. In such cases, various errors will appear, and AceSEF, as it deals a lot with URLs will be one of the most affected extensions.

Thats why Joomla! has added a variable for this in configuration.php file (not AceSEF's one), called $live_site.

If you're having problems with AceSEF enabled then you should check this variable by opening the configuration file and check if the value is like:

var $live_site = 'http://www.joomace.net';