Problem with wbadmin backup

I have my computer set to backup to a separate drive once a week
automatically using wbadmin. Normally it works fine, but sometimes it fails
with this error from the event log:

"The description for Event ID 546 from source Microsoft-Windows-Backup
cannot be found. Either the component that raises this event is not
installed on your local computer or the installation is corrupted. You can
install or repair the component on the local computer.

If the event originated on another computer, the display information had to
be saved with the event.

The following information was included with the event:

The substitution string for insert index (%1) could not be found"

Anyone know what might be going on here? Thanks.