In chapter 2, of "jQuery UI Cookbook", there are some issues with category sorting in IE 10. Thanks to Dave Sharman for providing the solution.

jquery.ab.autocomplete.js

$.widget( "ab.autocomplete", $.ui.autocomplete, {

    _renderMenu: function( ul, items ) {

        var that = this,
            currentCategory = "";

        // This should be returning integers, not booleans.
        items.sort( function( a, b ) {
            if ( a.cat > b.cat ) {
                return 1;
            }
            if ( a.cat < b.cat ) {
                return -1; 
            }
            return 0;
        });

        $.each( items, function( index, item ) {

            if ( item.cat != currentCategory ) {
                that._renderCategory( ul, item );
                currentCategory = item.cat;
            }

            that._renderItemData( ul, item );

        });

    },
    
    // The rest of the widget customization...
    
});