jQuery tabs function suddenly fails

As of this morning, the jQuery tabs function stopped working on our site. There were no file or plugin or theme changes at all.

I have an include file that’s been working for almost a year, but today I’m getting a console error on this statement:

jQuery(document).ready(function($) {

       // News sidebar tabs
       $( "div.tabs-nohdr" ).tabs({
           show: {
             opacity:'toggle',
             duration:'normal'
            } 

       });

The console error is “Uncaught Type Error: undefined is not a function.”

I checked out the page source and the jQuery library is correctly being called before the tabs function call.

Any ideas why this may have suddenly stopped working?