Tested on IE9, Firefox 12.0 Beta, Chrome (doesn't render at all).
www.thinkche.com/new/services.html

Click on Need Us Now button in header for example. This is the first time I've used the extension so any help would be greatly appreciated.

Hello Mike and welcome to DMXZone support forum.

Seems like in your own css file there is a rule that overwrites the css file of the lightbox.

Please open the following file:
www.thinkche.com/new/HTML5_thrColFixHdr.css

and edit the following properties that way:

.content {
    float: left;
    height: 400px;
    margin-left: 0;
    margin-right: 10px;
    padding: 10px 0;
    width: 252px;
}

Should become:

.content {
    margin-left: 0;
    margin-right: 10px;
    padding: 10px 0;
    width: 252px;
}

Regards : Vulcho.

Excellent. That worked perfectly. Thanks you for your help.
Mike