The exact following code fails when using jQuery 1.3.2 but not in earlier versions of jQuery (I tested 1.3.1, 1.3 and 1.2.6).

var myDiv = $('<div><p>My Paragraph</p><h2>My H2</h2></div>');
alert (myDiv.find("h2").length);
alert (myDiv.find("p,h2").length);

The second alert is never shown due to that the code inside jQuery breaks when the search includes 'p' in the filter.