We recently moved our central SQL server to new SAN hardware and at the same time upgraded from SQL2005 to SQL2008. Once this was done we noticed that our TFS Reports were running against old Warehouse data.

Checking the TFS Application Tier event log we saw:

TF53010: The following error has occurred in a Team Foundation component or extension:
Date (UTC): 21/10/2009 10:27:25
Machine: TFSAT
Application Domain: /LM/W3SVC/287244640/Root/Warehouse-2-129005451884971104
Assembly: Microsoft.TeamFoundation.Warehouse, Version=9.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a; v2.0.50727
Process Details:
Process Name: w3wp
Process Id: 2716
Thread Id: 2848
Account name: MYDOMAINTFSSERVICE

Detailed Message: Cube processing runtime error: rnMicrosoft.TeamFoundation.Warehouse.WarehouseException: The following database is not accessible in the Analysis Server: TfsWarehouse at Microsoft.TeamFoundation.Warehouse.OlapCreator.ProcessOlapNoTransaction(Boolean  schemaUpdated, UpdateStatusStore updateStatus, Server server, SqlTransaction transaction)
   at Microsoft.TeamFoundation.Warehouse.OlapCreator.ProcessOlap(Boolean schemaUpdated, UpdateStatusStore updateStatus)
   at Microsoft.TeamFoundation.Warehouse.AdapterScheduler.RunCubeProcess()

The problem was missing rights on the new 2008 Analysis Service instance. The quick fix was to give the MYDOMAINTFSSERVICE account administrator rights on the instance (SQL Management Studio, Connect to Analysis Service Instance, right click on instance, properties, security, add the user). Once this was done I could force a reprocess and all was OK