fine uploader - Error when attempting to parse xhr response text in fineUploader -

i bay fine-uploader version 3.3.0 now, , integration lib in site think uploads make working ok, no! see error javascript console:

[fineuploader] sending upload request 0  [fineuploader] xhr - server response received 0  [fineuploader] responsetext =  

and error firebug:

[fineuploader] error when attempting parse xhr response text (syntaxerror: json.parse: unexpected end of data) 

at line error: jquery.fineuploader-3.3.0.min.js(line 148)

i use params:

$(document).ready(function () {     $('#uploader').fineuploader({     request: {         endpoint: '/upload/'       },     classes: {         success: 'alert alert-success',         fail: 'alert alert-error'          },      text: {         uploadbutton: '<i class="icon-upload icon-white"></i> file target'       },        validation: {       sizelimit: 31457280         },                  debug: true      });   }); 

if write sizelimit: 10485760 - right ok working! file uploads finish. if write sizelimit: 31457280 file not uploads end, process break 2 or 3%. me! bug? please me somebody!

the following log message:

error when attempting parse xhr response text (syntaxerror: json.parse: unexpected end of data)

generally indicates server not returning valid json response. caused unexpected error server-side. note must return valid json response server. if using ie9 or older, sure return response code of 200 well.