Automatic mailbox switching fails, Mail Source Agent log contains "Critical error found" (4262304)

Automatic mailbox switching fails, Mail Source Agent log contains the error "IsReadyToSwitch Informational 2092 Synchronization status: Critical error found"

The following can be seen in the Mail Source Agent log along with the above Switch error:
"10/18/2011 11:10:47 AM MailKernel::ExportSource Informational 2049 Current '\BlackBerryHandheldInfo\BlackBerryCalSyncState' (Server: 'SourceServer', SourceKey: '2EBBE1181C927F4C97C261A589AA1D1E0000441514F1D').
10/18/2011 11:10:47 AM MailKernel::LogStatus TraceMsg 2040 Folder 'BlackBerryCalSyncState', sync type: [0x10 - Hidden messages], steps 1 of 1 done, sync aborted - False.
10/18/2011 11:10:47 AM CFolder::Synchronize Error -2147220732 The client operation failed. - MAPI_E_UNEXPECTED_TYPE (Microsoft Exchange Server Information Store) File: 'aeMAPIFolder.cpp' Line: '562' (Folder: 'BlackBerryCalSyncState', SourceKey: '2EBBE1181C927F4C97C261A589AA1D1E000001514F1D')
10/18/2011 11:10:47 AM MailExport::SynchronizeContent Error 2032 Cannot synchronize messages in the folder '\BlackBerryHandheldInfo\BlackBerryCalSyncState'. Messages type 32.
10/18/2011 11:10:52 AM MailKernel::IsReadyToSwitch Informational 2092 Synchronization status: Critical error found."

 

-This error indicates that the agent cannot get information about changes in this folder. If the agent receives this error for a folder, it raises the flag to prohibit switching (critical error found) and automatically purges the stream for this folder to provide that it is re-processed from scratch at the next pass, preventing switching.
-On the next pass, the agent fails on this folder (BlackBerryCalSyncState) again. Something inside the folder may be corrupt.
Getting the state of changes in a folder, the agent relies on ICS, a Microsoft interface that returns the MAPI_E_UNEXPECTED_TYPE error (-2147220732). The folder may look just fine when you open it with Outlook and do some conventional operations, but our agent sees a problem that may be specific to programmatic access through ICS.

Resolution 1
-Perform some Exchange offline Maintenance, which could repair the corruption within the folder, or the folder properties,

Resolution 2
-Unsubscribe the mailbox from the BlackBerry Services, thus removing the folder from the mailbox, then enable the user's BES account on the target side,