From jQuery 1.3.2 to 1.4 the detection of the XHR object has changed. In 1.3.2 every IE uses the ActiveXObject if available. In 1.4 every IE uses the ActiveXObject only if the location protocol is 'file:'.

This causes a problem in IE7, because in IE7 the implementation of XMLHttpRequest is a little bit buggy and in IE8 it seems ok. When you open a new XHR in IE7 with an absolute URL with a protocol and use the XMLHttpRequest object it fails with an error: 'Access is denied'.

IE7 with XMLHttpRequest: fails | IE7 with ActiveXObject : ok

IE8 with XMLHttpRequest: ok | IE8 with ActiveXObject : ok

Take a look at the attached test case, just upload it to any webserver.

Suggested fix #1:

Change the XHR handling so every IE uses the ActiveXObject if available.

Suggested fix #2:

Look for absolute URLs bevore opening the XHR and add a missing protocol.

Suggested fix #3:

Extend the XHR handling so that every IE uses the ActiveXObject if available and the protocol is missing or 'file:'.

Possibile solution:

I would prefer fix #3, so here is my fix which is also inlcuded in the test case. The file is named jquery-1.4.fix.js, just compare it with the 1.4 tag.

One problem i have is that i cannot differentiate IE7 and IE8 by the used object. So if the protocol is missing or 'file:' the IE8 will use the ActiveXObject also.

Best regards,

Sören

Some code:

Extended XHR handling

xhr: window.XMLHttpRequest && !window.ActiveXObject ?

function() {

return new window.XMLHttpRequest();

} :

function(protocol) {

if (window.XMLHttpRequest && protocol !== "file:" && protocol !== true) {

return new window.XMLHttpRequest();

} else {

try {

return new window.ActiveXObject("Microsoft.XMLHTTP");

} catch(e) {};

}

},

Create the request object

var xhr = s.xhr(protocol);