I have had an on-and-off backup issue with msdb database in SQL 7.0 server. When I manually uncheck "truncate log on checkpoint", the whole databases are backed up OK. Later, it resets to checked again. And backup failed with error below:

Backup set description: "msdb full backup"
Backup Type: DATABASE - Back Up Entire Database
Backup started on 6/20/00 at 4:30:14 PM.
Database msdb
Database filegroup from msdb

An error occurred on a query to filegroup msdb..PRIMARY.
^ ^ ^ ^ ^
SQL Server returned the following error message:

BACKUP LOG is not allowed while the trunc. log on chkpt. option is enabled. Use BACKUP DATABASE or disable the option using sp_dboption.

^ ^ ^ ^ ^
Unable to open the item msdb?PRIMARY - skipped.
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While it is simply not convenient to clear the setting by hand, I wonder if there's way to fix it. I noticed the msdb didn't reset its property after a successful db backup. There're lots of scheduled jobs running at night which might do some tricks on msdb, I don't know. It's hard to find out.

Anybody has a clue?