For the last week I've been getting erros in the Application log of my CAS/HUB server. I get 8-10 per day and they are MSExchange Common 4999 immediately followed by Microsoft Exchange Serv 5000 errors. Here is the 4999 Error: Watson report about to be sent to dw20.exe for process id: 2644, with parameters: E12IIS, c-RTL-AMD64, 08.01.0240.006, WS, M.E.D.Storage, M.E.D.S.Folder.ExecuteMapiGroupOperationMethod, System.NullReferenceException, 4ceb, 08.01.0311.001. ErrorReportingEnabled: True For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp. Here is the 5000 Error: EventType e12iis, P1 c-rtl-amd64, P2 08.01.0240.006, P3 ws, P4 m.e.d.storage, P5 m.e.d.s.folder.executemapigroupoperationmethod, P6 system.nullreferenceexception, P7 4ceb, P8 08.01.0311.001, P9 NIL, P10 NIL. For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp. I looked around and one of the recommended solutions was to install Exchange 2007 rollup 2, but I'm already on rollup 4. Some articles also claim that the problem could be with Transport servers and Entourage clients. I did create a mailbox last week that is being accessed by an Entourage client, but I already have 5-6 mailboxes that were getting accessed by Entourage clients. Ideas? Eric C.

Hello Eric, As you said, you are already on UR4, do you mean that SP1 UR4 or just RTM UR4? SP1 UR5 is also available, you may try by installing that. http://support.microsoft.com/?kbid=941421

I'm on SP1 UR4.Can I install SP1 UR5 on my CAS/HUB server without installing it on my mailbox servers or vice versa? It's not that I'm going to do it that way, I just want to know if I can.Eric

The basic sequence is to update first CAS then Hub and then Mailbox but its recommended to keep all the level same or in short-period of time.