No more User can log in to NLB-Terminalserver

Hello,

I configured Net-Load-Balancing on a Terminalserver Enterprise Edition via
nlbmgr and activated the session manager on the same machine. I don't
installed any user licenzes and now temporary licenzes are granted (its only
40 days from installing the server).
Now the Problem: the first 15 or 16 new users can login to the
cluster-ip-terminal-server, but every further user can't login. He gets a
"connection failed on network proplems"-error, but can login on unique IP of
terminal server. The first 15 users can login anymore on the cluster IP.

The Cluster-IP: 192.168.110.130
1. Terminalserver unique IP: 192.168.110.131 (+session manager installed)
2. Terminalserver unique IP: 192.168.110.132 (not installed, come soon)

Do you have any ideas?

Kind regards