Do you use the GRE-Plugin or the old Mapi-Integration? Later is not supported with Exchange 2010 and above.
DP 9 Support Matrix only states this regarding Single-Mailbox Restore:
Backup and restore of single mailbox, folder, and DAG are supported only through MS Exchange Granular Recovery Extension.
If you use VSS or E2010 Integration you should have no problems saving the Archive Databases.
