Terminal Server disconnects new Clients

I have a Win2K Terminal server with approximately 20 remote users of which 10 are either Win2K or WinXp and does not require a CAL. We have a 10-CAL license for remote users.

When I recently tried to add additional WinXP Pro or Win2K clients, the terminal server immediatly disconnected them. Shouldn’t they be “free”? One of the Win2K had previously been connecting via TS Client and was moved to the local network and now connects via the local LAN. When I try to access the TS from this PC using the TS Client software with the local IP address, it too gets disconnected. What am I doing wrong?

Thanks in advance.