Coding Error Detected

Clicking on a checklist as a student results in:
Coding error detected, it must be fixed by a programmer: PAGE->yui_lib() is not available any more, use YUI 2in3 instead, see MDL-34741 for more information.

I edited the checklist->locallib.php file and changed the yui2 to yui2in3 and the error went away, but when I look at the checklist now as a student, the checklist items do not appear. Also when I click on Add your own items there is no place to add anything.