Hi Chris, The slider does not need any additional dependency...
First question: are you using a wicket-jquery-ui-theme dependency or a custom one? In case of the second option, this might a version issue, even if it's supposed to be backward compatible... They released a new version some days ago and I am not yet up-to-date... Please also double check if jquery-ui.js and jquery-ui.css are well included and rendered (no 404) in your page. Best regards, Sebastien