Just moved to a new server, everything seem to went fine. The only thing is that any users with "admin" rights on the back-end of Magento just see the image below but staff are fine who dont have administrative permeations in back-end. Ho could I debug this!!
Set developer mode to true and set display errors to 1 in
Mage::setIsDeveloperMode(true); ini_set('display_errors', 1);
It should tell you what the error is
This is normal permission error. 1. Clear cache in /var/cache/* 2. Set default permission for your site on new server then try again.