user profile deleted

This is on a Windows 2000 unit. IBM Intellistation M-Pro.
All service packs and updated from Microsoft have been applied.
This week this problem stated.
The user have had user profile for several months.
This week when they log on okay. They log on
again and their profile is deleted and creates a new profile.
These user have user or power users right on this PC.
All administrator users profile are not effected on this PC.

I do not want to set all user with administrator rights.

I have checked Microsoft’s about this and no results for this
problem.

I will not like rebuild this unit now.

Please help.
Thanks