Random domain account lockouts

Hello,

We have a Windows Active Directory 2003 domain at the default functional level with a few NT4 domain controllers some of which are on WAN links.

Over the past 24-48 hours, we have suddenly gotten a lot of complaints that user accounts are being locked out even though the users have not logged out and logged back in. People who have just been working at their workstation all day without any logon or logout events suddenly have locked accounts in the AD-users and computers MMC.

All the domain controllers in the Headquarters building are getting their time from a GPS radio clock which is still working and serving SNTP. Has anyone run into something like this

Thank you.