TypeError: jQuery(…).knob is not a function

This error I’ve seen right at first time I had installed it. It had been gone when I deactivated and activated all WPMU plugins. And now it has come back when I just updated the plugin:

TypeError: jQuery(…:wink:.knob is not a function

http://movimientosesenciales.com/en/wp-content/plugins/coursepress/js/coursepress-front.js?ver=1.3.4

Line 32

I`ve tryed desactivate and activate it already.

What does this jQuery conflits means? How can I fix it, please? Any hook?