I've looked into the "admin/sources/base/ipsController.php" file on line 306 and the software is trying to execute and read your class permissions. I assume this is to read and validate your permissions as an admin when logging into the admin control panel.
Try to upgrade your files from the existing forum software using this download:
Go into your host's phpmyadmin, go into the admin_core table, and look for an issue related to your permissions.
If you still have access to the admin control panel and allowed to access the membergroups section, try to make a new admin group, set all the permissions your admin account has, and set your account to this new membergroup. If you already have other admin member groups on your forum already and can't access the admin control panel, you can change your membergroup via the core_members table. Edit the existing tables for your account and change the member_group_id to the same id as another admin membergroup.