Renamed Domain - Clients Still "joined" to old domain, can't open Group Policy Management on Server

Question

Performed a Domain Rename as per the following instructions:
http://www.bauer-power.net/2011/05/renaming-windows-domain-with-rendom.html#.U4OZRPmSyTM
and then after these issues I have gone through the related technet articles starting here:
http://technet.microsoft.com/en-us/library/cc794793(v=ws.10).aspx
specifically the Fix Group Policy Objects and Links.
But still I have the following issues:
At least for group policy clients believe they are on the old domain - despite even having renamed the computers with the new domain name.
When I perform a gpresult the output file shows as being connected to the old Domain - despite manually going into computer properties and renaming the computer with the new domain name...
CN=Allister Wade,OU=Users,OU=Home,DC=NEWDOMAIN,DC=local
Last time Group Policy was applied: 27/05/2014 at 5:36:31 AM
Group Policy was applied from:      finch.newdomain.local
Group Policy slow link threshold:   500 kbps
Domain Name:                        OLDDOMAIN
Domain Type:                        WindowsNT 4
On the server I cannot open Group Policy Management on the single Domain Controller as it is looking for a DC on the old Domain:
Even though it has listed the new domain in the root of the management console when I attempt to expand it out I am prompted:
"The specified domain controller could not be contacted. This affects the following domain in the console.
Domain: olddomain.local
The error was:
The specified domain either does not exist or could not be contacted."
I can select to remove the domain from the console but this does nothing - as said it already shows the new domain in the console.
Far as I am aware the clients should not even of needing renaming or changing the domain, but were having authentication issues before I did this. Not sure what I have done wrong here..?

Answer 1

Client's NSLookup shows "UnKnown" as DNS Server so thought to check DNS out.
This is result of dcdiag /test:DNS.
Directory Server Diagnosis
Performing initial setup:
   Trying to find home server...
   Home Server = finch
   * Identified AD Forest. 
   Done gathering initial info.
Doing initial required tests
   Testing server: Default-First-Site-Name\FINCH
      Starting test: Connectivity
         ......................... FINCH passed test Connectivity
Doing primary tests
   Testing server: Default-First-Site-Name\FINCH
      Starting test: DNS
         DNS Tests are running and not hung. Please wait a few minutes...
         ......................... FINCH passed test DNS
   Running partition tests on : ForestDnsZones
   Running partition tests on : DomainDnsZones
   Running partition tests on : Schema
   Running partition tests on : Configuration
   Running partition tests on : NEWDOMAIN
   Running enterprise tests on : NEWDOMAIN.local
      Starting test: DNS
         Test results for domain controllers:
            DC: finch.NEWDOMAIN.local
            Domain: NEWDOMAIN.local
               TEST: Delegations (Del)
                  Error: DNS server: finch.olddomain.local. IP:<Unavailable>
                  [Missing glue A record]
         Summary of test results for DNS servers used by the above domain
         controllers:
            DNS server: 203.12.160.35 (<name unavailable>)
               1 test failure on this DNS server
               PTR record query for the 1.0.0.127.in-addr.arpa. failed on the DNS server 203.12.160.35               
         Summary of DNS test results:
                                            Auth Basc Forw Del  Dyn  RReg Ext
            Domain: NEWDOMAIN.local
               finch                        PASS PASS PASS FAIL PASS PASS n/a  
         ......................... NEWDOMAIN.local failed test DNS