During focus event, link classes are hidden in IE7

Very curious bug that I've only seen in IE7 (IE8 works fine, as does Chrome):

I have my autocomplete defined so that it will add a css class to whichever suggestion was chosen (and it will wipe that class from all the other possibilities):

$('#searchbox').autocomplete({
  source: itemNames,
  focus: function(event, ui) { //highlight as user scrolls through options (keyboard up/down)
    $("ul.ui-autocomplete li.ui-menu-item a").removeClass("highlight");
    $("ul.ui-autocomplete li.ui-menu-item a").filter(function(index) {return $(this).text() == ui.item.value}).addClass("highlight");;
  }
});

While the addClass works fine, the removeClass has no effect at all - you can see this is you set breakpoints and step through these two lines. The result is that all of the elements become highlighted as you scroll through.

Further curiosities:

If you try to read the existing css classes on the link elements within this function, they're blank:

$($("ul.ui-autocomplete li.ui-menu-item a")[0]).attr('class')

All of this works outside of the autocomplete event, e.g. if you run this in the JS console manually, all the highlighted classes will be cleared:

$("ul.ui-autocomplete li.ui-menu-item a").removeClass("highlight");