I'm trying to install Pluto Core from the KickStart cd and I have an error when installer connects to the pluto web site.
The target PC has 2 network cards, one of them connected to internet via a proxy server (and without DHCP server), the other used for local network.
How can I configure the installer in order to use a static IP address and proxy server (if I choose not use dhcp server during debian installation, the installer doesn't ask me for networks parameters 
)
I can't picture your scenario above at all in my head, so I'll describe how things actually work.
The Debian installer (before it ejects the CD), regarding networking, it first checks for a DHCP server to give it network parameters and if there is no DHCP server on your network it asks you for manual input. It won't ask you beforehand if you want either DHCP or manual.
The 2nd stage install (after CD eject and ) will ask you if you want to run a DHCP server on the Core. Network is already configured from 1st stage install.
Currently you don't get asked explicitely about proxy servers, but, if you're patient enough, those web inquiries will timeout, one at a time, and the installation will continue from the disc. All needed packages are on the disc anyway. We plan to introduce an "offline mode" to prevent these timeouts altogether, but we're not there yet...
