Linux Permissions mistake has stopped scanning of database.

When I copy new music to my Linux (ubuntu 12.04 lts server) from my macbook the permissions are wrong so I have to run chmod to change the file permissions to 755.

Sadly, today my finger slipped & I changed all the permissions to 755 from / (root) downwards. (instead of just the music folder). The immediate effect was that the new music scan failed (Slim::Schema::Storage::throw_exception (122) Error: DBI Exception: DBD::SQLite::st execute failed: unable to open database file).

Can anyone advise what permissions I need to change to recover the situation.
Perhaps surprisingly, Logitech Media Server (v 7.7.3) is still running.

Obviously, I have other server permission issues so any general guidance would be appreciated.

Thanks,

JohnC