Open
config.php in a text editor such as Notepad++, and copy and paste this code at the top, after "
<?php".
Code:
define('DISABLE_HOOKS', true);
Save the file and upload it via ftp, and overwrite the old config.php (You can make a backup of your old config.php if you want to).
config.php is located here - "forum_root>includes>config.php"
Just incase if you have trouble finding config.php.
Then see if that fixed the problem. If it did, then the problem is with one of your addons you have installed and enabled.