Best posts made by Culture20

Figured it out!
Short answer: disabled IPv6 (and allowed NFSv3)
Long answer: On the server, set all the ports for nfsv3 to manual static ports, added the new iptables entries; Nada. Just for giggles, set a static address on the laptop with FOS USB, unplugged the server from the network and plugged both machines directly together, NIC-cable-NIC. Nada. Disabled the firewall on the server. Nada. Pings still worked, ssh from server to FOS USB worked, so the cable was working. Completely disabled IPv6 on a whim, and mounts from the debug console worked. Restarted iptables, and everything still worked. plugged the server back into the wall, walked the laptop to another location with a different subnet and several physical routers in between, and it still worked. Thanks for letting us know about the nfs version!