Login failed for user 'Domain\UserName'. [CLIENT: IP address] with SharePoint Farm | Deleting SSP Shared Service Provider

Of course when you get this error in SQL server, you thought that there is a process which is trying to connect with SQL Server with wrong user name or password. But with SharePoint Environment and when you delete SSP and its associated database, you will get this error and the reason is: when you delete SSP, SharePoint does not delete the JOB which is responsible for deleting expired sessions so this job is working each minutes and try to connect to SSP database, therefore you should delete this job manually after deleting SSP.