What means "martian source"?

Hello! I just installed a DSL-Router that I finished and tested at home into the company's LAN. Only one system can reach the Internet that functions as standard-gateway for all other systems, running some Virus-Scanner on windows NT 4.x. Directly on its console internet works pretty fine but every packages sent to it from the LAN don't go through. The only message shown on the LX-gateway is: "KERNEL:... martian source ..." from the IP-adress pointing to the LAN from the virus scanner system. What does this martian source stuff mean and where does it come from? Thank you for your answer in advance. -- Freundliche Gruesse kind regards Ingo