I'll check, but here is some more background.
I moved the firewall to a new computer. The old server was always accessible. And the other server on the network is readily accessible. I did a fresh install of RH7.0 on the new server (same version on other two servers). Everything ran fine for the first few days, then we (family) started getting the "Network is busy" error.
FWIW I do have a switch and a hub installed. But again, the other server and the old firewall worked without a problem. That leads me to believe I've set something incorrectly when I installed RH/Samba.