Thanks for your quick answer, leupold
i was able after windows restart to get the Administrator role displayed, and when i log in as an admin (member of that role), i am able to modify content, add pages, etc However the admin tab is missing.
i went to the tabs table, found it (by filtering portal id, and name admin) and its settings are all normal.
on a localhost, i have a dnn, i added a category called test and i assigned it to be the admin category on that portal.
when i logged in as admin (after restart), also in this case the admin tab is not showing.
thanks