Something very strange has occurred on our production SQL database. Users connecting via Windows authentication appear to have lost all access to the master database. By default, all logins have the default database set to master. So when you connect using SQL Server management studio, they get the error:
"Cannot open user default database. Login failed error 4064".
What's also worrying is that we have a group called "COMPANY - SQL Administrator" which has sysadmin rights and users in this group also get the same error. Worse, they don't appear to be system administrators anymore...
If they change their default database to something else, they can connect and then work on the database, it's just the master database that is problematic.
I'm not even sure by what mechanism windows authenticated users get access to the master database. Is it something hard coded in or some property that's got changed?