Installed Native File Access for Mac on a 5.1 server.

The first workstation can login fine. When I try to have a second
workstation login I get the following message:

Unknow user, incorrect password or login is disabled. Please retype the
name/password or contact the server's administrater.

It was suggested that I check NMAS trace. The first login show
everything OK - successfull login. The second attempt does not appear on
the trace, like it never got there. The trace did not change.

What do I need to do?