Alright, I know you said you OVERWROTE everything by re-uploading. For whatever reason, I've come to find when helping others around here, that things don't always get overwritten.
All the .php extension files that are in the /arcade/ directory should be deleted. THen deleted the arcade.php that is in your forum root /forum/arcade.php
Once you've deleted those, then go back and upload the php files like you just did.
I know it sounds stupid, but its been the solution for my issues in the past and some others that I've helped. Maybe we can break this curse of yours.