Logon being denied...sometimes

When a user, who is not an administrator, tries logging on the error, "The local policy of this system does not permit you to logon interactively" displays.  I've tried all the different fixes from the Microsoft website but that doesn't seem to matter.  Here's the catch though, roughly every other day or so the users can log on.  Is it possible that the two domain controllers that are running on the domain could be pulling their weight back and forth? This is on a 2000 domain.  

Thanks