RE: SQL Backup failed with exit code: 669

SQL Backup generates a log file for each process that it runs. The default folder where the logs are stored is C:\Documents and Settings\All Users\Application Data\Red Gate\SQL Backup\Log\<instance name> on Windows 2003 and older, and C:\ProgramData\Red Gate\SQL Backup\Log\<instance name> on Windows Vista and newer.

Could you please post the contents of the log file for the backup that failed?