Is the CMS code from PowerCMS?
It sounds like error reporting is turned off.
Add the following code at line 1 to turn error reporting on:
if the CMS Code is from power cms:
in the WA_CMS/WA_CMS.php file, comment out the securioty assist include line:
//require_once( "../WA_SecurityAssist/Helper_PHP.php" );
the security assist helpers are used for the live edit functionality, this will create a conflict on pages that have security assist applied.
If you want to maintain live edit on the other pages of you site you can create a copy of the WA_CMS.php file and comment the security assist line there, but leave it intact in the the other version. then in the developer notes for the security assist pages, attach the WA_CMSCopy.php page instead of the one that has the security assist include intact.