LTSP Login failure

[Global Profesional Services]

> I have a small 10 student lab and we are unable to login to the server 
> as thinclient. We get the boot screen and the login screen, but when a 
> properly instituted user give a user name and a password the system 
> fails to accept the login. The server will accept a direct login but 
> won't from the thinclients.
> There is no error mesage. The system simply default back to the 
> initial user login info???

Is there an solution for this problem??? Please Help??