problem of using network-manager-vpnc

[Xin ZHOU <Xin Zhou sim hcuge ch>]

Hello,

I'm new user of linux and I'm using Ubuntu 7.10.

Followed by some tutorial on internet, I've installed 
network-manager-vpnc and vpnc. Then I see the interface.
Compare with the interface in windows, it seems that it does allow to 
configure the transport (ex: the protocol or the port)

But I assume that by default they are configured.

And then I start the connection. The connection succeeded, but the data 
is not communicated.

I don't understand why, because normally if the connection is 
established, there should have no problems.

What can the problem be? How can I search for the cause of the problem.
Because that there is no much behaviour our error message that I can 
provide.

By the way, the server side of VPN succeeded to detected my connection.
So the connection is established.

Any idea for that?

cheers, Xin