http://blogs.msdn.com/b/ramaprasanna/archive/2009/09/16/invalid-object-name-sys-configurations-microsoft-sql-server-error-208.aspx 

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When you use Microsoft SQL Server Management Studio 2008 to access SQL Azure, if you get the following error

Cannot connect to <server name>

Additional Information:

An exception occurred while executing a Transact-SQL Statement or batch.

(microsoft.sqlserver.connectioninfo)

Invalid object name ‘sys.configurations’. (Microsoft SQL Server, Error: 208)

Then it is highly probable that you are entering the credentials in a wrong window.

Open the SQL server management studio 2008, CANCEL the credentials window that pop up.

Click on ‘New Query’, that’s the windows you need to enter your credentials in. Don’t forget to change the database name.

It should work !!