[jQuery] Background image position?!

[PaulC]

I have a pop up div on our sites home page. The content changes based
on the menu link the user clicked. A triangle tab should then move to
reside between the clicked menu item and the popUp.

This works fine of the dev server, but not on our live server (http://
www.pro-bel.co.uk/)

We've checked:

1 - The jQuery.js files and tried re-uploading the latest version,
both compact and normal.
2 - My scripts are the same on both servers.
3 - Both sites are on the same server though, just a difference
domain?!

To see the problem go to the live site: http://www.pro-bel.co.uk/ and
click on Routing & Control then Automation and Media Management then
Master Control. The blue triangle moves on the dev server to match the
position of the clicked link.

My Code:

$('div#solutions a.popUp').click(function(event) {
                        event.preventDefault();

                        /* Position tag */
                        var myPos = $(this).position();
                        var popup = $('#solutionTool');

                        // 327 is the Y position of the UL
                        // 24 is the aprox height of the li item
                        var myY = (myPos.top - 327 + 24) + 'px';
                        $('#solutionTool').css("backgroundPosition", "0px " + 
myY + "px");

                        return false;
});