Hello,
When I try to set a validation rule on a file, like this :
array('file', 'file', 'types'=>'jpg, gif, png'),
the only error message I get, is that the field is required >> OK
But when I add the allowEmpy like this :
array('file', 'file', 'types'=>'jpg, gif, png', 'allowEmpty'=>true),
The file is no more required, but I have no validation on the file type. 
Anyone no why ?
Thanks,
Maxime.