I have a situation where OWA was not working due to a conflict with a .NET update. I had to re-install IIS and following Microsoft KB 320202 I uninstalled the Client Access Role. There was an error about the OAB as it was on this server, re-created it on another server and un-installation preceded correctly. Upon re-installing the CAR however, it failed with: Event Type: Error Event Source: MSExchangeSetup Event Category: Microsoft Exchange Setup Event ID: 1002 Date: 7/01/2008 Time: 8:18:30 PM User: N/A Computer: Servername Description: Exchange Server component Client Access Role failed. Error: Error: This role cannot be installed because the following roles are not current: BridgeheadRole MailboxRole None of the exchange services start up now, for instance: Event Type: Error Event Source: MSExchangeSA Event Category: General Event ID: 1005 Date: 7/01/2008 Time: 9:00:56 PM User: N/A Computer: ServernameDescription: Unexpected error The system could not find the environment option that was entered. Facility: Win32 ID no: c00700cb Microsoft Exchange System Attendant occurred. and Event Type: Error Event Source: MSExchangeIS Event Category: General Event ID: 1121 Date: 7/01/2008 Time: 9:24:01 PM User: N/A Computer: ServernameDescription: Error 0x8004010f connecting to the Microsoft Active Directory. Any help/assistance would be appreciated.

It looks like your Exchange server cannot communicate with AD. is there any authentication errors or similar when bootin up your Exchange server

It appears that I am and that the Microsoft Exchange Active Directory Topology service is now missing.Event Type: ErrorEvent Source: MSExchangeISEvent Category: General Event ID: 1121Date: 8/01/2008Time: 8:44:16 AMUser: N/AComputer: ServernameDescription:Error 0x8004010f connecting to the Microsoft Active Directory. Event Type: ErrorEvent Source: MSExchangeISEvent Category: General Event ID: 5000Date: 8/01/2008Time: 8:44:16 AMUser: N/AComputer: ServernameDescription:Unable to initialize the Microsoft Exchange Information Store service. - Error 0x8004010f. Event Type: ErrorEvent Source: Service Control ManagerEvent Category: NoneEvent ID: 7003Date: 8/01/2008Time: 8:43:34 AMUser: N/AComputer: ServernameDescription:The Microsoft Exchange Transport service depends on the following nonexistent service: MSExchangeADTopology

If your "Microsoft Exchange Active Directory Topology service" is not running then almost nothing will work on your exchange installation. is the service still there, can it be started? make sure that your server is asking a DNs server containing AD information and not a DNS server on Internet when doing internal lookup.