Occasionally, but more often than I'd like, AJAX calls just don't work in IE (testing in IE9)
Sometimes, the request is logged as sent in the Network tab of Developer Tools, but stays "pending" indefinitely and is never actually received by the server.
Other times, the request comes back with an HTTP code that is unlike anything I've ever seen: well into the 12xxx range...
No other site I've been on that uses AJAX has this problem, so why am I getting such issues?