Add new Field Button not working

I did a new install of CFS plugin into my WordPress.

Clicking on the Add new field button is not working for me.
(nothing happens)

I checked my Javascript console and see this error:

TypeError: $(...).sortable is not a function
[Break On This Error] 	

update: function(event, ui) {

fields.js (line 39)

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WordPress 3.5.2
PHP 5.3.19
Apache
Mozilla/5.0 (Macintosh; Intel Mac OS X 10.7; rv:22.0) Gecko/20100101 Firefox/22.0

— Active Plugins —
A5 Custom Login Page 1.9.1
CiviCRM 4.3
Custom Field Suite 1.9.6

http://ww.wp.xz.cn/extend/plugins/custom-field-suite/