If you are on the NAVT List page, please take a look at the source code (using the Browser); do you see more than 1 line between the <head> and </head> tags that include the jQuery script?
There are a couple of possibilities:
1. Another jQuery script is being included in the HTML page. NAVT uses an older version of jQuery and that is by design. At the time I wrote NAVT, I used the jQuery script that was available at the time. I haven't upgraded it because the newer one is not compatible with NAVT. It matters not, because the NAVT List page belongs to NAVT and there shouldn't be any other plugins including a newer jQuery script; but it happens... Plugin developers don't typically check to make sure that the scripts they include are only for the pages that belong to their plugin.
Although, this does not explain why an older version would work where the newer version doesn't. Very few changes were actually made to the new version and none of them involved the java script.