SMB - domain login from XP not working

I have been testing using my MacOSX 10.5.3 server as PDC for Windows XP machines. I set it up on my test server with no problems. Enabled the SMB service, promoted it to a Primary Domain Controller and then a few other minor tweaks and away we went. I got mapped home folders and login script work really quickly. Because of this success I decided to integrate it into a server roll out I am doing at the moment with an Xserve and OSX10.5.4. I setup the SMB service promote it to a PDC and everything is perfect. I get a clean built Windows XP SP2 machine connect it to the domain, reboot, go to login but I get an error saying that "Windows cannot connect to the domain, either because the domain controller is down or otherwise unavailable or because you computer account was not found....".
After check things several times as well as other people confirm various options I am lost.

To add further confusion I went back to my test server removed my XP machine from the domain and re-added it to start testing my problem and holy cow I got the same error message.

The only difference is the 10.5.4 update I did after I setup my test server must have changed something thats stops me from logging in. Can anyone help??