How To Overcome
SSO is not configured
Failure when SSO has not been setup via Central Administration
Critical error logged in ULS with error code.
If SSO is not configured then configure from Central Admin.
SSO Wrong Version
SSO config setting or master secret has changed and change has not reflected.
Not applicable. Self healing error.
Failed to connect to SQL Server
Creation of the SSO database fails.
Critical error logged in ULS with error code.Error logged in application event log.
Check SQL connectivity. Check permissions for the account running the MS SSO service.
SharePoint Central administration virtual root not found
The SSO folder under 12\Template\Admin\SSO does not exist. This check performed while configuring master secret server. Either a call into Configuration.ConfigureSecretServer via OM or the UI page to configure SSO can throw this error.
Error logged in ULS with error code.
Or error returned to calling function
Repair the product installation.Most likely the files were not copied properly
Web application not running with windows authentication.
When a custom webpart is placed on a page in a non-windows auth web app. SSO CANNOT WORK WITH FORMS AUTHENTICATION.
Or error returned to calling function.
Check authentication providers for the web application. If you have a requirement to have the web app behind FBA, then SSO cannot work.
SQL Server not supported.
If the SQL server specified to host the SSO db is not greater than or equal to SQL Server 2000 SP3.
Check SQL Server patching and version numbers.http://support.microsoft.com/kb/321185
Minimum required is SQL Server 2000 SP3
Failure to connect to the Microsoft Single-SignOn Service.
Failure to connect to the MS SingleSign On Service. Either when the service is not started or the service has a logon failure.
Error logged in ULS with error code
The above information is indicative of the errors that you may encounter while working with Single SignOn on MOSS 2007. This is only for troubleshooting purposes.
Recommended Reading for March and April (click here for previous recommendations). Lots of useful content