Registered Server window does not show Database Engine or Local Server Groups

I am running SQL Server Management Studio 2012 on a Windows 7 machine. After a failed attempt to import my registred servers from SSMS 2008, the icons for Database Engine and Local Server Groups are not displayed in the Registered Servers window: the Registred Servers window is empty.

As such I cannot register a server from the SSMS GUI, by right clicking the Local Server Groups.

How can I restore the Database Engine and Local Server Groups items?