Hi Yuri,
Not understanding what you are trying to do. Surely by setting the
survey to private, it dissapears from anonymous view? Why would you want
to set the survey to private and allow anonymous users, or are you
trying to set the survey to require authentication as well as hiding it
from anonymous view?
I think you're getting an attribute error, as if allow anonymous is not
selected, then any user trying to fill in the survey will get checked
against the local acl_users in the survey.
Cheers
Michael