small business server +user connection problem

Hi to all.
In my office there is a server withsbs 2003.
About 10 users are connected to it But occationalt one of the user can’t access its folder on sbs.After some time without do anything it run well.On that user without him everybody can login in.Why do this.Sba can’t connect more than 10 users at a time.
Thanks in advance. Hope I will get a answer from you as soon as possible.