We are having a problem with the Offline Address Book. We are running W2008 for the CAS and the Hub Transport on one server. W2008 for the Mailbox on a 2 server cluster. On the CAS, in IIS, the OAB folder is there, but there is nothing in the folder. So there is no address book for clients to download. This is a new Exchange install, which has not been put into production. OAB on the CAS in Exchange Management is set to the OAB(default web site). Has anyone had this problem? Any help would be greatly appreciated.

Is your CMS configured as a server creating OAB files? Then looks like a known issue and Microsoft seems to be working for fix. OAB generation on a CCR cluster will fail with error 1021 Issues with web OAB gen for Exchange 2007 CMS on Server 2008 If you have another non-clustered server thenchange the OAB generation server to it or you can install another standalone server for workaround.