*MSSQL/SQL Server Management Studio: The server principal is not able to access the database

The error message you may get in MSSQL Management Studio:
The server principal 'A' is not able to access the database 'B' under the current security context (Microsoft SQL Server, Error:916)

Description of the problem:
This problem occurs with the SQL Server 2008 RC0 tools. When using SQL authentication, you can connect to the SQL server, but you cannot expand the Database tree. This results in the error above.
The problem lies in Management Studio itself and not in the SQL server on our servers. See also this solution, where this is also described.

Solution:

1. In SQL Server Management Studio, show the Object Explorer Details window by choosing View, Object Explorer Details in the menu (or F7)
2. Under VIEW, choose Object Explorer Details and click Databases

In the right-hand pane, right-click the column headers name/policy health state/recovery model/etc. Then switch off the collation column. If you do not do this, you will not see any databases and you will get: Microsoft SQL Server Management Studio 2008: Error 916