KJBweb - 9:37 am on Jun 24, 2011 (gmt 0)

What script is the site running upon, are you sure the script is configured to run upon the "www" version of the domain and not the "non-www" version?

Furthermore, have you checked any .htaccess rules that could be rewriting these requests?

SEO wise, your current situation is better than having both enabled; decide on either "www" or "non-www" and rewrite either accordingly using .htaccess rules.