SecurityException when making ajax call from only a certain machine?

When a certain machine tries to access my website, all AJAX calls fail. This happens for all browers on this machine, and no fire开发者_如何学Cwall or anything of the sort seems to be enabled. What could be the issue here? Opera tells me that the AJAX calls are returning a SecurityException.

What could POSSIBLY be happening to cause this one machine to fail on AJAX calls?

Do not use the full URL of your website in AJAX calls.

For example, suppose

http://example.com and http://www.example.com point to the same resource. If you give your AJAX calls the URL www.example.com/ajax.do, your calls will fail if the user browses the site from the first location.

Could it be that your site requires a login, and the AJAX Calls are not carrying over the session, for example because the browser has cookies disabled?

You may also want to post some more information about the site in question and whether that machine can access normal web pages on your site.