TCP traffic missing

My powerbook no longer seems to be receiving all packets that go over my network. I like to be able to see what's going on on my network, but now when I run EavesDrop, or Interarchy, all I see are packted destined for, or comming from my powerbook. On several instances I've used them to track down a highly active computer that's been slowing the whole network down. I was using my laptop on a public network a few months ago so I turned on the firewall allowing only internet through about the same time the problem started. I have since turned the firewall off but I'm still not seeing any other traffic. No hardware has been changed from the time it was working till now so I'm pretty sure it's a software setting somewhere.