Local Authantication service failed

dear all:
i have windwos 2000 advanced server with service pack 4. i am facing with lsass.exe service that block local authantication after 15 or 30 minutes and in event viewer give a error is
”
Event Type: Error
Event Source: LsaSrv
Event Category: Devices
Event ID: 5000
Date: 10-02-2006
Time: 11:30
User: N/A
Computer: server
Description: The security package Negotiate generated an exception. The package is now disabled. The exception information is the data.”

i did visit microsoft web site to view solution for this problem but i am not able to get any significent solution. please adviced for this critical problem, your cooperation would be highly appreciated.
thank you