I was able to reproduce this. Loading ioncube loader as Zend extension on PHP 5.3 cause 503 error on all ioncube encoded apps. It works fine with PHP 5.2.11 and others. Not sure if this is a litespeed issue ot ioncube loader libs (it works under apache in the same environment) Tested on 2 servers and could be reproduce. I'm going to check with IONCUBE people to see if they can find anything in the mean time.