Troubleshooting SRV Record Registration

1. Verify that the DC is trying to register the correct records. To do this, stop the "Netlogon" service on the DC and then delete the "Netlogon.dnb" & "Netlogon.dns" fiies located in the %systemroot%\System32\Config folder . Then start the netlogon service. Verify that the "Netlogon.dns" file contains the correct SRV records & verify that these records have been updated in DNS.

2. If the records did not update correctly , examine the system event log for errors. In particular , look for events with event IDs 5774, 5775 & 5781. Each of these event IDs indicates a problem with the SRV record registration.

For more info See this http://support.microsoft.com/kb/259277

SRV Records Registered by Net Logon

http://social.technet.microsoft.com/wiki/contents/articles/7608.srv-records-registered-by-net-logon.aspx

Using nslookup for verifying the SRV 

cmd---nslookup
set q=srv
_ldap._tcp.dc._msdcs.trusteddomain.com
_ldap._tcp.gc._msdcs.trusteddomain.com
_ldap._tcp.pdc._msdcs.trusteddomain.com
_ldap._tcp.dc._msdcs.trustingdomain.com
_ldap._tcp.gc._msdcs.trustingdomain.com
_ldap._tcp.pdc._msdcs.trustingdomain.com

Ensure that DNS pointing is correct on all DC, you may refer following to configure the same.
http://abhijitw.wordpress.com/2012/03/03/best-practices-for-dns-client-settings-on-domain-controller/ 

You may try to restarting NETLOGON and DNS service on DC to recreate missing SRV records.
How to verify that SRV DNS records have been created for a domain controller
http:/support.microsoft.com/kb/816587 

See following articles for causes and prevention- The Case of the Missing SRV Records
http://blogs.technet.com/b/askpfeplat/archive/2012/07/09/the-case-of-the-missing-srv-records.aspx 

A Complicated Scenario Regarding DNS and the DC Locator SRVs
http://blogs.technet.com/b/ad/archive/2008/08/08/a-complicated-scenario-regarding-dns-and-the-dc-locator-srvs.aspx