See? This event id= 18456 errors were not stopping and "Failure Audit" part panicked me. But one moment.. Everything was working ok? no service interruption, moss was fine!
So i just logon to SQL Server Management Studio to Sharepoint DB see what was going on on SQL error logs.
Login failed to Genelssp_db!!
But.. Genelssp_db belonged to a Shared Services Provider (SSP) which we deleted a few days ago!
Then with further investigation, found out that there is a job belonging to those dead and long gone ssp which was trying to delete expired sessions. GenelSSp_DB_Job_DeleteExpiredSessions
I disabled it and everything went fine..
The errors are gone.
I dont know why moss orphaned those job because I deleted this SSP via central administration and it was a succesfull deletion..