I've never seen this before, a BT update on Windows Update:
Update for BizTalk Server 2009 (KB2252691)
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.