Microsoft has released an update for Microsoft Enterprise Single Sign-On v4

This update corrects an assembly registration that causes a failure when .NET 4 is present on the system.

This update fixes an issue that prevents the ENTSSO service from starting, after installing .NET Framework 4. The registration of an assembly used by the Enterprise Single Sign-On Service to access SQL Server does not specify the correct version of the .NET Framework. When .NET Framework 4 is installed, the assembly will try to use the newer framework and then fail to load.

  Update for Microsoft Enterprise Single Sign-On v4 (KB2252691)