Policy Manager

I have a problem with NETWARE 5.1.
There are 25 Users Licenses installed on server and I have 15 workstations and I receive a message on workstation: Policy Manager(5.00-015) error#c0001006 and say that the total amount of licenses are used. I see in Monitor that there are some connections with NOT-LOGGED-IN.
I don?t know how resolve this problem or if I have to buy some additive licenses. Thanks.