Doesn't work on what end? The server or the client? I think Sterling's is a good guess, it's probably being cached, but you should try to give us as much information as possible so we can do more than guess.
Great wit and madness are near allied, and fine a line their bounds divide.
How where you able to solve this issue. i run into the say problem with IE 8. my code will work in every other browser but IE 8. I believe the request is stopping at "reqObj.open("GET",url, true); from the debugging report.