I get this error when bpchat is activated. I have a theme called mantra that is in use. Haven't had any issues so far except that theme-my-login and BPchat seem to have a conflict.
Fatal error: Call to a member function get_page_permastruct() on a non-object in /home/content/92/9657392/html/wp-content/plugins/theme-my-login/includes/class-theme-my-login.php on line 489
I had to manually remove your plugin via ftp to gain back access to my site. So temporarily I have both plugins deactivated
If you figure it out and can post the code I will be able to fix it myself by inserting what code needs to be changed/added.