Hello,
Please proceed like that:
- Each DC has one IP address in use and one NIC card enabled
- Choose a healthy DC / DNS server
- Make each DC points to the chosen DC as primary DNS server
- Make sure that each DC / DNS server points to its private IP address as secondary DNS server and 127.0.0.1 as third one
- Make sure that needed ports for AD replication are not blocked: http://social.technet.microsoft.com/wiki/contents/articles/active-directory-replication-over-firewalls.aspx
Once done, run ipconfig /registerdns and restart netlogon on each DC you have.
For the server, make it points to internal DNS servers as primary and secondary DNS servers.
Use nslookup to make sure that all is okay with DNS resolution.
Also, make sure that needed ports for AD authentication are not blocked:http://technet.microsoft.com/en-us/library/dd857231.aspx
If the problem persists then disable all security softwares that you have and check results.