We recently installed windows security updates on our windows 2003 servers in our domain. Our AD domain consists of 1 Win 2003 Primary domain controller, one Exchange 2003 server and 1 windows 2003 print server. All servers appeared to reboot fine after the updates except for the Exchange server. We cannot start the Information store service now, it times out after attempting to start the service and says "MS exchange information store service fails to start in a timely manner " We made sure the dependancy services are started, and even ran a KB hotfix from Microsoft. When we tried to re-install exchange to repair exchange, we are getting errors referring to a possible issue between AD and DNS. The exchange server and the PDC(DNS server) can ping each other by name, so it seems the DNS is working. This Exchange server is internal and has no external DNS resolution. Any advise would be greatly appreciated.