After installing Visual Studio 2010 Get Could not create SSOSQL. To fix the problem, reinstall SSO or try 'regasm SSOSQL.dll' from a Visual Studio command prompt.
I rebuilt my laptop recently with Windows 7 and installed AppFabric, .net4, VS 2010, etc.
When I came to configure BIzTalk 2009 I got the error in the subject line because the SSOSQL assembly needed to be re-registered.
Follow the instructions here to get it to work http://tomas-simonavicius.blogspot.com/2010/02/sso-service-failed-to-start-after.html