I am having trouble with cisco vpn (but probably is a general VPN problem) as it is blocking local LAN access while it is running.

Turning this off on the client does not help, since the server C (which over I have no control) forces that local LAN is disabled and all routes are going into the VPN tunnel.

I am now trying to circumvent this restriction. Since I saw that cisco VPN runs better on linux and windows, I want to install VPN and other tools I need on a dedicated workhorse server A (linux), to which I open a session with NXclient (terminal client) from client B. Machine A then opens up a VPN tunnel to Server C and (supposedly) kicks me out, since all traffic from A is going into the VPN tunnel to C and disconnects my client B.

Is there a way to get around this? I know that this is a security risk for Server C and opens up the network in a way that responsible of server C wanted to prohibit with this LAN local access disabled in the first place, but I will be using a firewall to close off any entrance into the network.

I just don't want to stink up my winXP installation with yet another thing that patches directly into the "kernel" and brings my XP installation one day closer of dying miserably and needing a reinstall, that is why I wanted the thing installed on linux, which is far better in my opinion for getting serious work done.

Anyone know how to tweak the routing table to disable what the VPN client is doing to my machine?

Well, looks like a toughy this one. Nobody knows the answer so far.
I found out that there is a native linux (open source?) implementation of a Cisco compatible VPN access client called vpnc (at least that is what the package here in debian sarge is called)
I will give that one a try, maybe it allows to enable LAN access.

Markus