'session disconnected' error

Hi,
I'm using an Acer A100 tab running Andoid 3. Using PocketCloud free 1.2.182

I'm trying to connect via WiFi to a Microsoft Terminal server that remote desktop on it.

I've set this up as a manual connection but as soon as I tap 'connect I immediately get a 'Session Disconnected' error.

The windows server I'm trying to connect to is Windows 2008 R2. NLA requirement has been disabled on the server ('allow any time' selected). The user has been added to the 'remote desktop users' group on the server.

I've checked the server logs and I don't even see an authentication attempt being made.

This server uses a custom port for RDP (TCP:1751) but I've specified that in the connection settings. I have a telnet utility on my table and I've verified that I can telnet to the server okay on that port.

The server does have GPOs applied to it (as it's internet facing), but none that I would think would cause this - are there any known to cause problems?

I did successfully connect to a Windows 7 desktop inside my LAN.
thanks