Lost user profiles in NT Workstation

We are running various Dell platforms (Mostly GX1’s) and NT 4.0 SP6. As of the last few months we have random occurences where NT? appears to lose the system user profile. It creates a new one and renames the old profile
whatever the users name is followed by .bak. (username.bak)
We have various “remedies” to fix it after the fact but no one here has been able to come up with a cause or permanent solution to the problem. A search of the Microsoft Knowledge base has been fruitless also.
Does anyone out there have a fix?

please email me at:
mearsg@mdot.state.mi.us if you can help!

THANKS!