Active Network Connections

I have a problem with Parallels on Snow Leopard when using Juniper's "Network Connect".
As long as the Parallels Adapter in the Network System Preferences are active,
Network Connect will lose 2/3 of the packages (for a kind of explanation see: http://www.kahmann.net/apple/2009/09/16/tutorial-juniper-network-connect-os-x-106-snow-leopard/).
When deactivating these Adapters
everything works fine. I have found:

http://forum.parallels.com/showthread.php?t=89905

and as far as I understand the thread, these adapters are superfluous???
Parallels works even without them? So, why are they there? Can I simply
keep them disabled? Or do I have to reactivate them when using Parallels?

But then I will again have problems when using Network Connect which I need
when Windows is started via Parallels.

Victor