I ran Firebug on the page (your live one) and saw but one small css issue that should not have created the slowdown you are experiencing.
Expected end of value but found 'font-weight'. Error in parsing value for 'letter-spacing'. Declaration dropped.
letter-spacing: 0px font-weight: normal;
template.css (line 61, col 34)
Maybe someone else will be able to determine the reason for the slowdown.