slow XP logon in win2k3 domain

I am havin problems with  extended logons times whilst logging on within my domain.  It is not effecting every computer.  The delay takes place whilst the computer and security settings are being applied.

I have checked the other answers on this:

http://www.windowsxpatoz.com/cgi-bin/performance/index.cgi?answer=1036283899&id=1036282433

Has been implemented

My DNS is setup the right way I believe. ie my DHCP points the the dns to the DC

Any other suggestions would be gratefully received

 I get the following error in eventvwr
#1202
Security policies were propagated with warning. 0x57 : The parameter is incorrect.

Please review the detailed log security\logs\winlogon.log under Windows root to troubleshoot the application of security policy.  

and
#1085
The Group Policy client-side extension Security failed to execute. Please look for any errors reported earlier by that extension.

Nothing I have tried works.




Are the following errors in the security\logs\winlogon.log to do with it?

----Reading Configuration Template info...
Error 13: The data is invalid.
 secreateglobalprivilege is not a valid privilege.
Error 13: The data is invalid.
 seimpersonateprivilege is not a valid privilege.
      Event audit settings are turned off.