Help, User Rights Assignment in Local Policies keep resetting

Hello, this is happening on a Windows XP Professional, SP2 fully
patched. It used to share files on the network but suddenly it stopped
doing so. After some reading I found that the User Rights Assignment
propery was missing the required values. So I added the accounts and
this allowed the computer to share files again.

This would work for a few minutes but five minutes later computer
trying to access the share could not because the settings were blank
again. I repeated the process of adding the values to User Rights
Assignment and they keep resetting.

Has anyone encountered this problem? How were you able to solve it or
work around it? Thank you.