Zend_Form_Element_File override getErrors(), hasErrors() and getMessages() to transfer the method to the adapter. However, the following functions are not overridden.

    addError()
    addErrors()
    addErrorMessage()
    addErrorMessages()
    setErrors()
    setErrorMessages()
    clearErrorMessages()

So for example "$errors = $form->getErrors();" after "$form->addError($msg);" does not work as expected but returns nothing.

Please make them work as expected, or just override those functions to throw the exception (if you do not have much time)