Cross-Origin Resource Sharing and IE9
If you want to save yourself an afternoon debugging. Please be aware that the onprogress event must be set on the XDomainRequest object.
If the onprogress event is undefined. Internet Explorer 9 will just abort the request.
For example:
var xhr = new XDomainRequest();
xhr.open('POST', 'http://example.com/resource');
xhr.onprogress = function() {}; // <-- IE9 will abort if missing
xhr.send();
This bug was introduced in the final (RTM) release of Internet Explorer 9. It does not appear in Internet Explorer 8 or any RC version of Internet Explorer 9.
See also MSDN on XDomainRequest.
