Try keep the rdp client connected through console. Use the following command to open the RDP Client in console mode :
mstsc /console
After the login, close the RDP client keeping the console logged.
Try to connect the VNC Client. It should show you a Win 2008 login screen, showing a user logged.
Grab the logged session and go on from there.
Another solution is to use an app like Teamviewer or Logmein .
Regards,
=FN=Fluidman