Forum Problem with domains with and without WWW
 

If I enter domain name like http://domain.com and login, it's redirecting to http://www.domain.com/register.php and after successful login it's redirect me to http://www.domain.com/forum.php or sometimes redirect me back to http://domain.com/forum.php

This is problem for some plugins, so I need to fix this - like it be before.... If I enter on site from http://domain.com , it should go to the http://domain.com/login.php and redirect me to forum home http://domain.com/forum.php and ALL of links "pull" from http://domain.com . AND if I enter from http://www.domain.com, redirect me on http://www.domain.com/login.php and to forum home http://www.domain.com/forum.php

Just not mix links with and without WWW!!!