loading............
 
tienes un error 406 
Código:
 <!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
<HTML><HEAD>
<TITLE>406 Not Acceptable</TITLE>
</HEAD><BODY>
<H1>Not Acceptable</H1>
An appropriate representation of the requested resource /enviarvoto.php could not be found on this server
.<P>
<HR>
<ADDRESS>Apache/1.3.37 Server at www.querubo.com Port 80</ADDRESS>
</BODY></HTML>
  osea el tipo de peticion que hiciste el servidor no lo acepta :p (a mi entender) 
ponle esto 
 Código PHP:
    function enviarVoto(){
    ajax=objetoAjax();
    ajax.open("POST", "enviarvoto.php", true);
    ajax.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded; charset=utf-8'); //<-- esto
    ajax.onreadystatechange=function(){
        if (ajax.readyState==4){
        alert(ajax.responseText);
        }
    }
    ajax.send(null);
} 
    
  
connection closed.