>> What version of VFP? Prior to VFP7, FOXUSER.DBF was single user. It can now be shared.
>
>We have VFP6. Why I don't have this problem with other applications used by many people at the same moment?

Maybe they each have their own copy of the FOXUSER.DBF or they're not using the resource file at all. If you have a CONFIG.FPW file with RESOURCE=OFF in it, FOXUSER.DBF isn't used.