XML DOM hacking in MSIE: halp!

[prog]

Righto, I just sacrificed a couple of hours on the altar of trying to get shit to work in MSIE. On the plus side, I think I can eliminate one of the third-party libraries I've been using; MSIE was barking at it, and I find that I can do the same thing it was doing using Prototype, which the application already depends on.

On the minus side, MSIE's XML API eludes me. Consider this code snippet. Given xml_request, an XMLHttpRequest object:

alert(xml_request.responseText); // This prints the correct thing.
var xml_doc = xml_request.responseXML;
var root_element = xml_doc.documentElement;
if (root_element) {
alert("I have a document element. I am a sane browser!");
}
else {
alert("I have no document element. I must be MSIE. Fuck.");
}

The initial alert() makes me sure that MSIE (as well as any other browser) is in fact reading the XML. I just can't do a damn thing with it after that; every attempt to peek into any DOMmish properties of xml_doc returns null.

xml_doc.firstChild and equivalent statements all fail equally (while succeeding on sane browsers). Wha?

Another good reason to drop the library I am dropping? It contains lines of code like this:

MWJ_ldD[MWJ_ldD.length-1].onreadystatechange = new Function( 'if( MWJ_ldD['+(MWJ_ldD.length-1)+'].readyState == 4 ) { '+oFunct+'(MWJ_ldD['+(MWJ_ldD.length-1)+'].load?MWJ_ldD['+(MWJ_ldD.length-1)+']:MWJ_ldD['+(MWJ_ldD.length-1)+'].responseXML); }' );

Holy hannah. That's no way to make friends.