First, you should try to make sure the box.js line always occurs together with the other script lines in our standard View Cart code like so:
<script language="javascript" type="text/javascript">
<!--
function EJEJC_lc(th) { return false; }
// -->
</script>
<script src='http://www.e-junkie.com/ecom/box.js' type='text/javascript'></script>
Also, while the problems you describe are unusual and don't ordinarily happen for most visitors using your site with an E-junkie cart, there's always the chance of ISP and general network routing issues that could be causing weird behavior unrelated to our own operations. When anyone's browser loads your page with E-junkie cart button codes, their browser first has to contact your main Web site's server to get your page, and then it has to contact our server to obtain the button images and our box.js script file, and their browser continues to communicate with our end whenever they interact with the cart itself.
At any moment, there could be network congestion or other routing glitches across the Internet between the user's ISP and our datacenter that do not affect their ISP's network routing to your main Web site server. Meanwhile, most other users with a different ISP or located in a different geographical area probably wouldn't encounter the same connectivity glitches, so their browser going through their ISP would be able to reach both our datacenter and your site's server without any problems.