If you look at the page source on the checkout page, do you see the uc_cim js and css included? You should see a couple lines like this:
<style type="text/css" media="all">@import "/sites/all/modules/ubercart/contrib/uc_cim/uc_cim.css";</style>
<script type="text/javascript" src="/sites/all/modules/ubercart/contrib/uc_cim/uc_cim.js"></script>Could you also clear your browser cache to make sure you're using the latest js file?