I have the same problem as you. But even if I add

$element->clearDecorators();
$element->setDecorators(array(
array(‘ViewScript’),
array(‘File’),
array(‘Errors’)
));
to my file element, i get the “no file decorator found” error… can you send me your solution? I also have my own decorator for my forms. Do I have to create my own Decorator for the file element? I thought he uses de default one, if I write it in that way… maybe you can help me :-)