I use this library to perform my AJAX calls and I've noticed that on MSIE 9, some AJAX (not all) would get aborted by the browser for no reason.
I've found this thread on StackOverflow http://stackoverflow.com/questions/15786966/xdomainrequest-aborts-post-on-ie-9 and tried the suggested fix and it seemed to work better (no more randomly aborted AJAX calls).
What I've done is define an empty function
xhr.onprogress = function () { };
in the first try...catch block of the ajax method.
Thanks for your time