The trouble is:
We have an instance, there are several databases. We have a login (uses Windows authentication, lets call it 'DOMAIN\user'), which is mapped to several DBs as public. When connecting to server under that login you can view all of these DBs except one. When trying to access this one, the error pops up 'Database is not accessible'. Under other logins it is accessible, and our 'DOMAIN\user' is mapped to it, has rights to connect to it (watched in permissions of DB), I even tried and made him datareader.
sp_helplogins shows, that he is user in this DB, and has several role memberships.
I tried to drop him and create again - still got the problem. The interesting thing is that there are users with identical rights, who can connect to DB. Any ideas/suggestions?