An unrecoverable error occurred. This form was missing from the server cache. Try reloading the page and submitting again.

You can check /var/log/httpd/error_log for more information like:

 “/filefield/ahah/xyz/field_upload_document/0”.

For resolving the problem just install the latest version of the Filefield module and edit “filefield_widget.inc” file for commenting below parameters:

 /*'#ahah' => array( // with JavaScript

       'path' => 'filefield/ahah/'.   $element['#type_name'] .'/'. $element['#field_name']

.'/'. $element['#delta'],

       'wrapper' => $element['#id'] .'-ahah-wrapper',

       'method' => 'replace',

       'effect' => 'fade',

    ),*/