Hi!
I have been able to use a SQL 2012 DB aswell and with the SQL Native Client 10.0.
In my case the problem was that the user set for the DB wasn´t set to owner. I had to login to the SQL Server,
start up SQL Management tool and go in under Logins and choose properties for the user created for the
composer database and make it db owner. It was only set to public in my case.
Cheers,
Erik