Worker treats are hung, in which order Black berry services needs to be restarted. If you are moving users within the same Exchange server, you will probably end up breaking the BES connection to the mailbox, Apparently version 4.0 BlackBerry is looking in LDAP server DN (distinguish name) therefore it is not able to locate the user mailbox. Anyway follow the order below when BES services needs to be restarted. This is best practice from RIM support.
Restart the Black Berry Services in this order below
Service establishes connections, Manages the connection to the wireless network for the BlackBerry Enterprise Server. Also routes data to handhelds that are connected through the BlackBerry Handheld Manager.
Establish connection to Exchange, Performs data encryption and compression services for all data that the BlackBerry Enterprise Server sends or receives.
Controls all other services, Monitors key BlackBerry Enterprise Server components and restarts them if they stop responding.
Other services can be started in any order,
When configured, sends alerts when events at the specified level occur on the BlackBerry Enterprise Server.
Converts attachments into a format that can be viewed on the handheld.
BlackBerry Database Consistency Service
Synchronizes data between the BlackBerry Manager database and user mailboxes.
Blackberry Mobil data service
Provides secure access to online content and applications on the corporate intranet or Internet through the BlackBerry Enterprise Server.
BlackBerry Policy service
Supports wireless IT Policy, service books, and third-party application delivery for the BlackBerry Enterprise Server.
Manages the connection to the wireless network for the BlackBerry Enterprise Server. Also routes data to handhelds that are connected through the BlackBerry Handheld Manager.
BlackBerry Synchronization service
Synchronizes PIM application data wirelessly between the handheld and the mail server.