We are using a extension "Groups Catalog 2".
A strange thing is, that our pages can't be shown for users that are logged in, but all pages a visible for users NOT logged in. I am not talking about the categories, but the CMS pages.
The same thing is with the search. A user that is not logged in, can use the search functionality, but the user which is logged in can't use search functionality. It just gives an ERROR 503.