Manipulating the dom after *-child selector may break sequent *-child selectors if the number of childs remains the same.

I think this is caused by caching in filter.CHILD, here:

var doneName = "child" + parent.childNodes.length;

Changing it to

var doneName = match[0];

(which i saw is set in preFilter.CHILD) should fix the problem.

Also, parent.childNodes.length is painfully slow on explorer. This change should speed up IE (and slow down the other browsers).