Strange transient error with Multi-file Upload

Question

I'm running grails version 2.3.3 on a local PC not on the internet at this stage.

I am building a multi-file upload process and I'm having what can only be described as 'transient' behaviour with this.

By transient I mean it has worked correctly for a while repeatedly uploading files successfully and then starts to fail consistently without me having changed any of the code.

The error is:

Error 500: Internal Server Error URI /VidPlay/fileUpload/saveMK Class groovy.lang.MissingMethodException Message No signature of method: org.apache.catalina.core.ApplicationHttpRequest.getFileNames() is applicable for argument types: () values: [] Possible solutions: getHeaderNames(), getMimeTypes()

Here is an overview of the code - firstly, the html for the upload form is:

            <g:uploadForm action="multiFileSave" name="mikeK">
            <fieldset class="buttons">
                <span class="pageHeader"><g:message code="Upload a New Picture" /></span>
            <g:submitButton name="Save" onclick="fileUpload.selectButton()" class="buttons" value="${message(code: 'default.button.save.label', default: 'Save')}" />
            </fieldset>
            <tr class="prop">
            <td valign="top" class="name">
                <label class="uploadFile" for="payload">File:</label>
            </td>
            <td valign="top">
              <input type="file" id="file" name="file[]" multiple/>
            </td>
          </tr>

        </g:uploadForm>

Here is the controller action that handles the upload or transfer:

    request.getFileNames().each{

        log.debug(  "getFileNames getFile: ")

        //for(  file in request.getFiles(it))

        request.getFiles(it).each
        { file ->

            // loop through all files selected
           log.debug( "multiFileSave - name: $file.name Originalfilename: $file.originalFilename contentType: $file.contentType")
          try{
               file.transferTo( new File( userDir, file.getOriginalFilename()))
               upFiles = upFiles + " " + file.originalFilename
               def pictId = PicturesShr.findByName(file.originalFilename)
               if(pictId) multiFileLst= multiFileLst + "|" + pictId.id                  
          }
          catch (Exception eWrite)
          {
             log.debug ("File Transfer error files: file.originalFilename Error: ${eWrite.toString()}")
             flash.message = flash.message + "File Transfer error files: file.originalFilename Error: ${eWrite.toString()}"
             failFiles = failFiles + " " + file.originalFilename
          }
       } // getFiles loop
    } // getFileNames loop

As I am doing all this on a local PC using Win 7.0 I can see that this it is a very artificial environment with the local machine acting as both a client and server at the same time. This leads me to think that my problem is some sort of machine or OS resource limit issue.

Alternatively, perhaps there is a cleaner way of getting the file information from the upload form into the action?

Note - this odd behavior has happened in two separate applications - I first introduced this file upload system into a development application and it worked correctly for a period and then started to consistently fail with the same error quoted above.

Would welcome any suggestions - thanks in advance.

-mike