No conversion from script to jsonp (chrome, safari & fireworks)

No conversion from script to jsonp (chrome, safari & fireworks)

From localhost I call a rest service (php) via cross domain using jsonp, it works on Internet Explorer but I got error on Chrome (21.0.1180.60), Safari and Firefox. Any idea or help is welcome.
Here is the code: 
  2. $.ajax({
  3.   type: "GET", 
  4.   url: urlroot, 
  5.   data: {}, 
  6.   dataType: "jsonp",   
  7.   success: function(resp){
  8. alert("mserver says: "+resp.message);
  10.   },
  11.   error: function(e, textStatus, errorThrown){ 
  12. alert('Error: '+errorThrown );    
  13.  
  14.   }
  15. });
Please tell me what's wrong