[jQuery] xml namespace problems

[Tony]

Here is the xml

<?xml version="1.0" encoding="utf-8"?>
<lib:catalog xmlns:lib="http://localhost/";>
  <lib:book name="bookext">
    <lib:user name="user">
                <lib:book name="bookint">
                </lib:book>
        </lib:user>
  </lib:book>
</lib:catalog>

The experssion
$('catalog > book', xml).each(function() {
// do something here
});
Does not work in IE6 and FF.

The expression
$('catalog book', xml).each(function() {
// do something here
});
Work in FF but not in IE6

The expression
$('lib\\:catalog lib\\:book', xml).each(function() {
// do something here
});

Work in IE6, but not in FF

Any help on how to solve this problem?
In my case catalog and book are parameters
Thank you in advance

Tony