SuSEFirewall and routing between internal networks

Hello! I'm using SuSEFirewall with kernel 2.4.7. I have two internal, private (192.168.x.x) networks, besides the world connection (to the Internet - third network card). Routing to the Internet works perfectly. All PCs in both nets access the Internet. But PC in each internal net cannot access the other internal net. It simple seems that SuSEFirewall is not routing the packets between the two internet nets... Does anyone know how to make this work? Is there any way to configure the box (or SuSEFirewall) to route packets between the two internal nets? Any suggestions would be welcome. Best regards, Afonso Infante.