I've been running BizTalk 2009 on my Windows Vista laptop, and suddenly today the Enterprise Single Sign-On Service stopped working. When I tried to start it manually, I got this error in the event log:
Could not create SSOSQL. To fix the problem, reinstall SSO or try 'regasm SSOSQL.dll' from a Visual Studio command prompt.
Error Code: 0x80131700
It turns out this error told me everything I needed to know -- except the location of SSOSQL.dll. Took me a little digging, but I found it here:
C:\Program Files\Common Files\Enterprise Single Sign-On\SSOSQL.dll
So, navigating to that folder in the Visual Studio Commmand prompt and running 'regasm SSOSQL.dll' fixed it right up.
The only lingering mystery is why the DLL got unregistered in the first place. I'm suspicious of Visual Studio 2010 Beta 1, which I installed yesterday. But I've got no proof of that.
(And yes, I do install a lot of goodies on my laptop.)