Please consult your php error log. You can determine where your logs are by viewing your php.ini and looking for error_log=. If you do not have error logging enabled you should consider turning it on, or turning on display errors temporarily.
Here are instructions for enabling displaying of errors:
locate and edit the /main.inc.php
On circa line 44 locate
#Don't display errors
ini_set('display_errors',0);
ini_set('display_startup_errors',0);
and change it to:
#Don't display errors
ini_set('display_errors',1);
ini_set('display_startup_errors',1);
This will make OST display your errors. Simply change the 1's back to 0's later once you are done.
