Work in FF, Safari and Opera not in IE

Work in FF, Safari and Opera not in IE

Hello,

I try to use jquery to manage a little hierarchical menu. It seems easy, and after 1 hour of scripting (first time that I use Jquery) it's working in FF, Safari and Opera.
It's not working in IE.

http://parquets-online.limax.lu/test.html


Thank's for your help I'm desesperate.

Laurent.