jQuery Forum

I'm using jquery 1.4.4 just fine, however when I tried to use 1.5.0 I get this very weird issue:
1. callback is automatically added to my url
&callback=jQuery15048196098537446064_1297079245499
2. and I get this parsererror status

According to the document, callback should be added only if the dataType is jsonp? My dataType is set at json:

$(this).ajaxSubmit({
              success: updateContent,
              dataType:  'json',
              error: function(jqXHR, textStatus, errorThrow) {
              $.fn.displayMessage('Error: ' + jqXHR.status + ' ' + jqXHR.statusText + ' ' + jqXHR.responseText + textStatus + errorThrow);
              }
             });