<nav> element (or any other new HTML5 element) with some content, and then try to append content to it.
var test = $('<nav>Test</nav>');
test.append('append'); /* Fails with an error in IE 6-8 */
Here is a simple test case showing the problem:
http://www.haprogszone.net/jquery_bug_ie6-8.html (includes the html5shiv but it doesn't seem to affect the problem)
This works in Firefox 6.0.2, Chrome 13, Safari 5.1 and Internet Explorer 9, but fails on IE 6, 7 and 8. Tested on Windows 7 (32bit). The problem occurs on every major version of jQuery I tested including 1.6.4.
Interestingly though (as shown in the above test case URL) the same error does not occur when the created
<nav> is first empty
var test = $('<nav></nav>');
test.append('append'); /* Works */
The problem does not occur when dealing with HTML4 elements instead.