Tried for weeks and weeks to connect to a Windows 2008 Server via remote desktop from my Xubuntu-12.04 laptop. To no avail. There were some steps required like setting up VPN with fixed IP, finding a remote desktop client and trying to connect to the server, so a lot of potential problem sources.
To cut straight to the point:
sudo aptitude install remmina
solved the problem.
Fast-IP-VPN was correctly configured, but the Ubuntu default remote desktop client rdesktop was refused by the 2008 server. What made the problem not so obvious was that the connection to another remote desktop at the same institution worked without problem, but that was a XP server. No one was aware of this and event the IT-support suggested rdesktop.
On top remmina comes with a graphical user interface and in Xubuntu an item in the system tray makes connection to a once correctly configured remote desktop a one-click affair.
Hattip to Jonathan Moeller and his The Ubuntu Beginner’s Guide.
A short howto remmina on ubuntugeek.com