FileUploadInterceptor not using internationalized error message, in acceptFile(...) method when File is null, it should use webwork.messages.error.uploading, as listed in javadoc.

validation.addFieldError(inputName, "Could not upload file");

should, i guess, instead be,

validation.addFieldError(inputName,
                 getTextMessage("webwork.messages.error.uploading",
                 new Object[] { "Could not upload file with input name ["+inputName+"]" },
                 locale));