simple javascript problem?

To He or She who dares take my simple challenge:

I have been given the task of writing a cross platform (IE 4+, Netscape 4+, Netscape 6+) Dynamic HTML menu system in JavaScript. I succeeded in making the program work for IE 4 (tested through version 6) and Netscape 6.1, but am unable to figure out why it does not work in Netscape 4.

At the following address you will find a ZIP archive containing the source code for the project: http://collegemans.net/menu.zip.

Any assistance is greatly appreciated. Thank you.

Aaron Collegeman for Collegeman Web Consulting.