Dropdown menus are currently broken in develop (future 8.x) if the first thing you do is leave the menu immediately by clicking outside of it. This will result in an error in chosen-jquery and the dropdown becomes unusable.
This does not occur if the first action is to select a value fom the dropdown menu.
This is not broken in 7.x, so could have been introduced by the jquery update. The code throwing the error is custom code we introduced to chosen for loading more roles.