Win 2k server Error.

my server works fine, i just get these eror messages exactly every five minute and they procced by a warning

this is the warning:
Sorce:SceCli
event:1202
Category:None
User:N/A
and here is the description it gives me:
Security policies arepropagated with warning. 0x534 : No mapping between account names and security IDs was done.
Please look for more details in TroubleShooting section in Security Help.

the is the Errori get:
Sorce:UserEnv
event:1000
Category:None
User:System
and here is the Description:
The Group Policy client-side extension Security was passed flags (17) and returned a failure status code of (1332).

thank you