Not only does the AM server and the SQL server appear to lock up but also the average disk queue length on the drive that houses the TempDB hits 100
The Clustered Index on the dbo.EmailAddressDisplayName table in the ArchiveManager database is bad.
Open SQL Server Management Studio and expand Databases > ArchiveManager > Tables> dbo.EmailAddressDisplayName > Indexes
Right click on PK_EmailAddressDisplayName (Clustered) and choose Rebuild > click OK on the Rebuild Indexes screen
This may take awhile to rebuild the Index, once it's complete restart the Archive Manager services
