Error: has no method 'curCSS'

I created a tags field in my forms and this field used to pre-populate with existing terms when the first letter was typed in using autocomplete. It no longer does this after an update. You can see here: http://www.collagenetwerk.nl/inschrijven/ (The field near the bottom called ‘Vaardigheden’ bellow ‘Extra’). Typing in the letter ‘c’ which has an existing term ‘communication’ results in the error:

Uncaught TypeError: Object function (e,t){return new v.fn.init(e,t,n)} has no method 'curCSS'

typing ‘q’ which has no existing term gives no error. I have tried a clean install with the same result.

What could be the problem?
Any help would be greatly appreciated

http://wordpress.org/extend/plugins/gravity-forms-custom-post-types/