hi all. i have DSL through qwest, and so i have an actiontec dsl
modem/gateway/router/whatever all in one. it has four ethernet ports.

i have two computers, one G3 mac running mac os 9.2 and one pc running
debian linux r3.1 (i owned the mac first, if that makes a difference).
the mac always connects to the net fine. here's the problem... if the
mac is connected, then the pc connects fine. if the mac isn't
connected, the pc won't connect. (dhclient tries to obtain a lease and
eventually gives up) if the mac and pc are both connected and i
disconnect the mac, the pc eventually loses its connection.

i'm totally stumped. any ideas? if not, does anyone have any suggestions
on where to begin to troubleshoot this mutha?

Are you sure both computers are using DHCP? If one has a static address then it may be conflicting with the other which would end up with neither working reliably. Try setting both to static as a test.