These errors indicate that the Archiving Task was deleted prior to it completing work, so messages still in the MSMQ etc. Each task has a unique reference linked to it. Could you paste the whole error from each event ID in so we can see the ID's. You could then run a SQL query script to see what the database has in it with regard to these entries :-
USE EnterpriseVaultDirectory
SELECT TaskEntryID, Name
FROM Task
You can then see if the TaskEntryID in the error matches any of these, I am guessing it isn't. There is an internal technote that can help you, but ideally you should open a support case to get some eyes onto your system to see what state your queues are in.
thanks
Mark