I have had the pleasure to be able to look at (and fix) a number of ZenMagick installations. If there is one thing that can really help you find out what goes wrong, it’s the following:

Create the file local.php in your zenmagick folder if it doesn’t exist yet and insert the following PHP:

<?php  @ini_set("display_errors", true); ?>

This tells PHP to display all fatal error messages in the browser. Usually this is enough to give you a good indicator as to what is wrong with the installation or template.

ZenMagick comes with a sample named local.in.php that contains (commented out) settings and commands that can be useful to get ZenMagick configured and logging set up so you’ll be able to read the logs even in a hosted environment where there is usually no (direct) access to the webserver’s logfiles.