This can be caused if there is an issue communicating with the CAS server over RPC.
Error may be present in the SpotlightRemotingServerNet.log
12/6/2012 3:00:13 PM: Process ID 668: Thread ID 4: Quest.Spotlight.SOM.Common.DomainSpecificLibraries.PowerShellLibrary.Exchange2007PowerShellHelper (IL Offset 0x5F): Finished executing command:get-queue -ResultSize unlimited -SortOrder '+NextHopDomain' -server server.domain.com
12/6/2012 3:00:13 PM: Process ID 668: Thread ID 4: Quest.Spotlight.SOM.Common.DomainSpecificLibraries.PowerShellLibrary.Exchange2007PowerShellHelper (IL Offset 0xB2): PowerShell error:Microsoft Exchange can't connect to the RPC server on computer "server.domain.com". Verify that you used a valid computer name.
OR
the Spotlight on Messaging Service account is not a member of the Organization Management security group.