Hi,
Are all your domain controllers up and functional?
If a domain controller loses connectivity to the forest, Knowledge
Consistency Checker (KCC) generates multiple event ID 1566 entries
which can quickly cause the event log to wrap.
DNS is one of the most common reason for failure to replicate
Check your sites, check that the proper IP subnets are associated with
the
proper sites, check your site links, and then check that the proper
sites
are in the site links you've created. I've seen these issues
specifically
when the sites were mistakenly added to the wrong site link, or no site
link.
Troubleshooting Active Directory Replication Problems
http://technet2.microsoft.com/Windo...5749-4e5a-a216-38f9faed53441033.mspx?mfr=true
Harj Singh
Power Your Active Directory Investment
www.specopssoft.com