Error 'Unexpected licence packet' with xfreerdp connection to Windows Server 2012

i am having the following problem with RDP connections on Xubuntu 14.04.1 LTS 64 bit:

I am trying to connect to a Windows Server 2012 Standard (64 bit). It's in a workgroup named 'WORKGROUP' (it that matters).

First of all: connecting with an Windows Administrator account (including 'attach to console') works! But unfortunately its not possible to 'attach to console' with non-administrator accounts.

At first, I tried Remmina (version 0.9.99.1) as root, but it gives me the error 'Unable to connect to RDP server xxx'. Of course, 'xxx' is the correct hostname of the server. console output is this:

# remmina
Remmina plugin VNC (type=Protocol) registered.
Remmina plugin VNCI (type=Protocol) registered.
Remmina plugin RDP (type=Protocol) registered.
Remmina plugin RDPF (type=File) registered.
Remmina plugin RDPS (type=Preference) registered.
Remmina plugin SFTP (type=Protocol) registered.
Remmina plugin SSH (type=Protocol) registered.
connected to xxx:3389
null server certificate
Unexpected license packet.

as i could find out, remmina uses freerdp in its rdp plugin, so i tried xfreerdp (version 1.0.2) next, which gave me the following error:

# xfreerdp -u rdptest xxx
connected to xxx:3389
Password: 
ERRINFO_LICENSE_INTERNAL (0x00000100):
An internal error has occurred in the Terminal Services licensing component.
Unexpected license packet.

The next thing i tried was rdesktop (version 1.7.1) with this output:

# rdesktop -u rdptest xxx
disconnect: Internal licensing error.

So it seems every rdp client produces the same error.

What I know of the windows account is: It is in the user group of allowed RDP connections. I even tried to change the users password to a simple one (the minus - is the only special character). A connection from windows computers does work.

Last thing i tried was the different encryption algorithms with xfreerdp, and the only one i was able to connect to server was nla, so xfreerdp --no-nla does not work.

There is another client called 2xclient, but its only available for 32 bit systems so thats no option. So if anyone has an idea what I can do would be great. I hope i gave enough information to check this out further.

I haven't had to deal with Micro$oft Licensing issues for a while, but if I remember correctly, if you connect from one of the Microsoft "Professional" Licenses (business edition etc) the license is included in the workstation license but for home Edition and Linux I think you need to purchase additional licenses...