Did you hve installed a PHP tracking or stats system on your website?
It sounds so. Cause of you errormessage. Or is 'ob_gzhandler' set in your PHP Ini file?
Add this in your mainfile.php before the include( line:

define('_OPN_SKIP_COMPRESSION','1');

This line should deactived the setting of the ob_start call.

I am really looking forward to using this program but I get an error at the bottom of my homepage that says:

ERROR [2] (null)() [ref.outcontrol]: output handler 'ob_gzhandler' cannot be used twice
FOUND IN [Unknown]
FOUND AT 0


Could anyone help me with this? It would be very appreciated.