form_validation.php displaying directly to the screen

[eluser]kimp[/eluser]
I have loaded form validation rules into the form_validation.php configuration file. The problem is that whenever a controller is instantiated the entire form validation file is displayed to the screen.

I found that it works fine if I open the config file with a php tag (<?php ...) however I don't think this shoud be required. Should it?

The rules are fine. The problem occurs even if I cut/paste the file contents from the codeigniter documentation.

I am using Zend Server on a Windows 7 PC.

Any ideas?

Thanks!

[eluser]intractve[/eluser]
All .php files anywhere in the codeigniter file structure start with the <?php tag and do not have the closing tag but just two lines of comments to denote end of document