Add this to the top:
<?php
ini_set("display_errors",1);
?>
That should give you the actual error instead of the general 500 error. Hopefully that will shed some light on the problem.
Your friends over here at WebAssist! These Dreamweaver extensions will assist you in building unlimited, custom websites.
These out-of-the-box solutions provide you proven, tested applications that can be up and running now. Build a store, a gallery, or a web-based email solution.