Problem with .ajax json return

Problem with .ajax json return

I am having a problem with the .ajax json return. I was using getJSON, but changed to .ajax and now getting error about returning the json. I am atempting to simply update some text fields with json data. I have changed this thing so much that I forgot what I had originally. So the code may not work... This is being executing on a IBM Series i(AS/400) thus the reason for the not too familiar code.

This is my code:
  $.ajax({                                                      
         async: false,                                         
         url:      'AJAX003R.pgm',                             
         data:     {VESSEL:vess,VOYAGE:voyg,BLNUM:blno},       
         dataType: 'json',                                     
         success:  function(json) {                            
           $("input#SXSCAC").val(json.SCAC);                   
           $("input#SXEORI").val(json.EORI);                   
           $("input#SXCCN").val(json.CCN);                     
           $("input#SXCAAT").val(json.CAAT);                   
           }                                                   
        }); 






My response is thus: 
{ SCAC:'ABCD', EORI:'1234567890', CCN:'Unknown', CAAT:'Unknown' }
    I am getting a jQuery error in jquery 1.4.2  @ 5252
try {
5252 xhr.send( type === "POST" || type === "PUT" || type === "DELETE" ? s.data : null );
5253 } catch(e) {
5254 jQuery.handleError(s, xhr, null, e);
5255 // Fire the complete handlers
5256 complete();
5257 }

The ajax was working. I get lost in the jquery syntax. Never sure when to use a "$" or not too.

Any help is most appreciated