If your ajax response includes a "Content-Type" header with the value "text/xml", Firefox expects the response to be valid XML with a single root element. If it is not, Firefox issues the "no element found" error.
As for the second error, it may be that in either of the following lines the value of "data" is not valid HTML or contains tags like <html>
or <body>
:
$("#addressresult").prepend(data);
$("#orderdetails").html(data);