Kunena 1.6.0 integrates the newest version of Mootools JavaScript library (1.2.4):
http://docs.kunena.com/index.php/Mootools_1.2.4

Unfortunatelly new version of Mootools is not compatible with jQuery UI Slider.

There is an event name collision in "slide" function (both provided by Mootools and jQuery), more info:
http://dev.jqueryui.com/ticket/4168 

We're working on fix for Captcha plugin.

Fixed in version 1.0.2