I am not sure because i havent tested but try these

you have
#categoriesContent A.category-top SPAN.category-subs-parent{
position:relative; left:-15px;
padding-left:15px;
background-image:url(../images/arrow.gif);
background-repeat:no-repeat;
background-position:-140px 4px;

}

maybe IE use twice the image from
and the A.category-topSPAN.category-subs-parent
why dont try just

SPAN.category-subs-parent{
position:relative; left:-15px;
padding-left:15px;
background-image:url(../images/arrow.gif);
background-repeat:no-repeat;
background-position:-140px 4px;

}


i know is not a tecnical opponion but some times works with IE