i cant see why it is not working on your layout, and I'm not able to reproduce the problem, but i think i have a workaround for you.
in the webassist/datepicker/events_results_datepicker_4/jquery-ui.css file,
edit:
/* states and images */
.ui-icon { display: block; text-indent: -99999px; overflow: hidden; background-repeat: no-repeat; }
to:
/* states and images */
.ui-icon { display: block; text-indent: 99999px; overflow: hidden; background-repeat: no-repeat; }