Hi Burkem5,
Thanks for the suggestions.
When pings from the PC to the module fail, "arp -a" does not show the module IP. As soon as I ping the PC from the module "arp -a" shows the module IP address and everything works for a few moments but as soon as I stop using the address for, say, 5 minutes the module get's cleared from the ARP cache and vanishes from "arp -a".
Using "arp -s <module IP> <module MAC>" on the PC to add a static entry for the module works, until I reboot the PC. Using a static IP for the module does not help as the PC still can't find a route to the module without some sort of intervention on my part.
Listening to network traffic on both the "wired" and "wireless" side of the network I can see the PC sending out ARP broadcasts for the module's IP address but they are not showing up on the wireless side. When I ping the PC from the module I can see it's ARP broadcasts on both sides and the PC's reply comes back (as it's now routed, not broadcast). I believe I can also replicate the problem using a laptop on the wireless side so it's not just these modules.
I've not had the chance to try resetting the Hub yet as I had other work to be getting on with and I can work around the problem for now by using a second accesspoint (old BT 2700HGV) on the network or "arp -s" to add a static route.
Thanks again,
Roger.