Rdesktop and network level authentication

Ok,

I now that I am not the first one to ask but I could not find any documentation anywhere.

I am running OpenSuse 11.2. I have rdesktop installed. When I am on my work’s VPN network, I can only remote into XP machines, not 7 machines.

I know (because I really think so) that I need to enable some Linux version of “network authentication level”. Is there a simple conf file I can change?

Thanks in advance for all of the support.