[jQuery] xml parse error onreadystatechange

[will]

I'm confused....why is the xml parse error being thrown when I'm
dealing with json?

if ( status == "success" ) {
// Watch for, and catch, XML document parse errors
try {
        // process the data (runs the xml through httpData regardless of
callback)
        data = jQuery.httpData( xml, s.dataType );
        } catch(e) {
        status = "parsererror";
        }

The call is:

$.ajax({ type: "POST", contentType: "application/json; charset=utf-8",
            url: "getColors.aspx",
            data: "{}",
            dataType: "json",
            success: function(data) {
                   $(dropdownSet).loadSelect(data);
                      adjustSizeDropdown();
             },
            error: function(xhr) {
                 $('#errorDisplay').html('Error: ' + xhr.status + ' '
+ xhr.statusText);
                 $('#errorDisplay').css('display', 'block');
    } });