I created a menu that works fine in IE but doesn't appear in Netscape.
One thing of note, I first ceated a demo version of the new menu using js files from v5.21 - all worked well. Since then, I have purchased another license for this menu and have installed the associated js files - upgrading to v5.62. Now the menu works in IE but not Netscape.
Current is 5.691. There was a fix in there specifically for NS7.x that had to do with doctype. While you're not using the specific doctype that was mentioned in the fix, it still might be a good idea to upgrade and see what happens.