Figured it out. samdoyle is correct. You can't make "cross-domain" calls. The definitions of acceptable and unacceptable differences in "domain" can be found here. (e.g. in Firefox, even different port numbers are unacceptable). http://www.mozilla.org/projects/security/components/jssec.html More useful info on working around this issue by Using a Web Proxy for Cross-Domain XMLHttpRequest Calls http://developer.yahoo.com/javascript/howto-proxy.html Thanks everyone for all your help! View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4070307#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...