You will have to fix it directly in the db
The function is
select acs_permission__grant_permission(:object_id, :party_id, :privilege);
party_id in this case is -1, priv is read, and you can get the object_id
for main site via
select object_id from site_nodes where parent_id is null;
(it's 2565 on the installs I have done lately).
