After upgrading to Service Pack 1, sometimes i got failed to login my server
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Although my below snaps mention SQL Server 2008/express I would suggest to check for the below points.
Check whether you need to put the local computer name prefix before your DB name

If you connect using Windows authentication with the account you've created when you create your DB instance you can troubleshoot with right click database --> Database properties and select the below security option.

Check sa login under security option by double clicking. You can change the password if required as below.
Also if you see USER MAPPING option on the same properties view, check it and makesure sa is checked into the database you want to login.

services.msc)