Active Directory Issues

Have Windows 2003 Activer Directory server which suddenly started having authentication issues, we have had some replication issues in the past where PDC will not fully replicate to BDC. but today it looks like they are sync'd up with Widnows 2008 AD server. But 2003 server still has all the AD roles. CURRENT Issue: 1. Exchange 2010 servers are not able to authenticate with AD, so I removed Front end Exchnage server from the domain and now trying to re- join the domain. 2. Rejoining the domain is throwing DNS errors. I have made sure DNS is running okay. It is able to resolve names and domain as well. I added a host entry in the Hosts file as well just to be sure. Getting following error when Joining the domain. Note: This information is intended for a network administrator. If you are not your network's administrator, notify the administrator that you received this information, which has been recorded in the file C:\Windows\debug\dcdiag.txt. DNS was successfully queried for the service location (SRV) resource record used to locate a domain controller for domain "[login to view URL]": The query was for the SRV record for [login to view URL] The following domain controllers were identified by the query: [login to view URL] [login to view URL] However no domain controllers could be contacted. Common causes of this error include: - Host (A) or (AAAA) records that map the names of the domain controllers to their IP addresses are missing or contain incorrect addresses. - Domain controllers registered in DNS are not connected to the network or are not running.