Following the update of WordPress perhaps a feature in one of the plugins has stopped.
Reviewing the page errors with the browser inspector shows the error
$.browser is undefined
I have also encountered the $.browser is undefined error when I took over a website and updated the jQuery references as a part of my initial actions.
With the introduction of jQuery version 1.9 jQuery browser was no longer supported.
To our rescue is a set of scripts called jquery-migrate. The aim of which is to add back in those missing functions. Allowing more time for the changes to jQuery to be incorporated.
To add migration support add
to the web page. Take care in its position on the page to get the sequencing right.
$.browser was used to determine which browser was in use, visiting the web page.