Eu tentei fazer assim:
I did the same thing in deleting the anonymous user from the Guest group. My problem manifested itself by showing NO forums to unregistered users. Some message like "No forums available" appeared to all browsers of the forum.
Not knowing how to edit mySQL, I didn't know what to do. What worked for me finally was a simple fix, but I have seen no reference to this elsewhere. So to restore the Anonymous user to the Guest group:
1. Login to the forum as admin
2. Get to the Administration Control Panel
3. Click Manage Users under Quick Access or the "Users and Groups" tab
4. Check the "Select anonymous user" box and click Submit
5. Use the "Select form:" dropbox, select "Groups", click Go
6. Use the "Add user to group:" dropbox, select "Guests", click Submit
Essa questão foi um usuário quem fez.