"Single sign-on authentication failed on database xxxx.fp7 using zzzz[fmapp]"
I have implemented Single Sign on and and users log in ok however in the server event log I see
Client ABC Single sign-on authentication failed on database xxxx.fp7 using zzzz[fmapp]
but the single-sign on did not fail, the user was logged in ok?
I have read http://help.filemaker.com/app/answers/detail/a_id/6785 but hat is different it is a Warning and it is reporting a username password authentication warning as opposed to a single sign-on warning.
I haven't been able to find any specific report of this particular message.
I think you are dealing with this issue: Authentication Failed log messages in Server 10
This is one of many acknowledged bugs that can be found in the Known Bug List here in the Report an Issue section of the forum.
It can also be downloaded as a database file from: http://www.4shared.com/file/8orL8apk/FMP_Bugs.html