Error on Scheduler Manager

I’ve installed joomla dhtmlxScheduler on 1.5.18 with no errors. When I try to configure it fails to load.

What could be the reason?

TKY very much safe for help.

Linux 2.6.18-128.1.6.el5 #1 SMP Wed Apr 1 09:19:18 EDT 2009 i686
Servidor wep: Apache
PHP 5.2.10
Server API Apache 2.0 Handler

public_html and subdirectory writable 777

Try to update it with next version