Why won't this url validate?

[geeves]

Hi guys.

Just launched my first site and there are pages which just wont validate.

http://ara.ifky.com.au

If you navigate to the contact page and try to validate the xhtml via the link at the bottom of the interface, w3 gives me the following error:

I got the following unexpected response when trying to retrieve :

500 Internal Server Error

Any help would be appreciated.

[aln_cms]

could it be to do with your .htaccess file?

Alan