I installed the plugin tonight and tried to set it up step by step. Fortunately I only installed it on my testing site. When I came to database security, I backed up my database. I then continued and I am not sure what did it, but my menus did not show anymore. So I restored the database according to this site...
and this is what happened:
Is there any chance that somebody can give advice regarding this mess.
(After all it also locked me out and blocked my IP, so I am in a mess! Cannot even log in via my control panel, but hope this will sort itself after 1 hour).