I have a maintenance plan that backups up my system databases and the transaction logs nightly. The backup of the data completes successfully, but I receive the following:
1. Database model: Transaction Log Backup (succeeds)
2. Database model: Verifying Backup (succeeds)
3. Backup can not be performed on database 'msdb'. This sub-task is ignored.

The maintenance plan exits at this point with error code 1.

When I run the extended stored procedure in ISQLW I receive:

(38 row(s) affected)

Server: Msg 22029, Level 16, State 1, Line 0
sqlmaint.exe failed.