Clean/SEF URL's error

There seems to be a problem whilst trying to use Clean/SEF (Search Engine Friendly) URL's. The reason for this is shown below:

Unable to use mod_rewrite rules

It appears that the .htaccess file is in place, however the Rewrite rules are not being using. This could be due to:

    * The Apache module 'mod_rewrite' is not installed and/or not enabled
    * Your 'AllowOverride' directive in your Apache config does not allow for overriding of FileInfo

For a more detailed troubleshooting, please refer to the README file or post a message on the TangoCMS Forums.