I've done some more testing and it seems that Chrome is the culprit. When opening the SM web page, the page appears quickly but it doesn't allow me to scroll or click on any link for about 2 seconds. It responds normally after the initial delay, but when clicking on another link the new page opens instantly but there is again a 2 second delay before it responds to scrolling or clicking.
Internet explorer is fine. I suspect as you do that it might be due to the Facebook plug-in which isn't working BTW.