wrap removes expandos (jQuery 1.2.1)

When you create an element (using document.createElement) and add
expands to it, they are removed when that element is used to wrap
another one.
Example:
http://www.texotela.co.uk/wrapexpandos.php
I use this method for my focusfields plugin, and as a result it does
not work in Internet Explorer if jQuery 1.2.1 is used.