When working with XML in jQuery a selector called $find can be used to find elements in the XML object that is loaded. I had a problem with IE7 and a webservice returning XML. The problem was that IE 7 didn´t recognize the returning XML as an [object] but rather as a string. Adding a dataType attribute to AJAX method solved the problem.
Solution reference: http://www.gammageek.com/2008/10/jquery-xml-in-ie.html