WinXP GPO in 2000 server

[PauloNet]

Hi all,

i´ve made something wrong when i aplied GPO to my domain.
All workstations (98 and 2000) are OK but two With XP had the following problem:
When i reboot (for the second time) any user including administrators loose the connection with the server. However i can still connect to the server if i logon with a local user and supply a network user and password.
The error message says "the system found a possible security problem. Make sure you can contact your domain controler"

Wath have i done wrong in GPO? Can i put it back the way it was?

Thanks all,

Paulo