In some situations you will get this error due to SPN settings. For example if you are doing disaster recovery testing to a new sever you may get an SSPI error while connecting to SQL Server. Even more odd is that you may be able to connect using SQL Server Management Studio but you can't connect via ODBC or OLEDB. There may be a temporary workaround that will probably allow you to get to the database.
Workaround: On each client computer trying to connect to the SQL Server, create an entry in each workstation's host file. The exact mechanism this uses to fix the issue is unconfirmed but it may be that using it overrides the need for the SPN.
While this isn't guaranteed to be fix for all cases it will most likely get you back up and running. This should not be considered a permanent fix. You should resolve the SPN or other issues in an ideal situation. However if you're having issues with old Windows machines running an unsupported operating system or if you're just doing proof of concept disaster recovery testing this should get you where you need to be to keep the lights on or production back up and running.
