Both known and common issues. Discussed here in the forum and mentioned on
http://www.publishermvps.com/Default.aspx?tabid=30 .
Issue 1:
It helps to understand that Publisher is designed to support IE
functionality and exploit it fully. Other browsers aren't a real concern.
This particular issue is due to VML in Publisher 2003. Firefox isn't built
for VML. If you look at the page source in Firefox you see that all the VML
code including the links of that nav bar is commented out by Firefox,
followed by it's replacing it with image file "image661.gif" which is a
static version of the menu. Under Publisher's web options you can turn off
the option to always use VML and then resave and republish and see if that
helps any. Let us know what you find.

Issue 2:
Now we are getting into more technical web stuff. Open your page in IE and
hover the cursor over a link on the left menu and look at the status bar of
the window. Now repeat this process hovering over the bottom menu. Do you see
the distinct differences in the links? The menu on the left has relative
addresses. The bottom menu has absolute addresses. The nav bar wizard always
uses relative in that menu. Frames will break relative addresses. The .org
domain frames the true location of the files. Talk to the hoster of the
framing about redirecting instead of framing.