What version of Enterprise Vault are you running?
What storage do you have? (NTFS / Netapp / Centera)?
what is the Vault Store Partitions Safety copies set to? (After Backup / After Backup (immediately for journaling) / Immediately After Archive)?
Has it ever worked for these users?
The pending items, do they show up in archive explorer or search.asp?
Is the Vault store these users belong to in read only mode at all?
When hitting store in vault, how long do you expect it to go to a fully archived item?
Do you have any warnings from monitoring in the morning saying x amount of savesets are awaiting to backup?
Are these users in Cache mode or non cache mode?
Have these users been moved from one exchange server to another recently?
Can you synchronize the users mailboxes manually?
Is there anything in the event logs regarding these users?
Can they open up previously archived email?
If you cancel operation on those items and re-attempt archiving, do they still stick in pending mode?
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