I have an ap810 configured to station infrastructure mode, connected to another ap810 (in AP mode) which is then connected via cable to a 2860 non-wifi router.

All devices connected to the AP mode ap810 work flawlessly, the ones connected to the station mode ap810 initially connect to the internet, but then fail after a few minutes never to reconnect again. There is nothing other than a factory reset of the ap810 and a reconfigure in station mode that will solve this, albeit briefly. I am pulling my hair out now.

Any ideas as to what is happening here?

If I've understood correctly you have one AP wired to the router and are trying to run the second AP via a wireless bridge to the first.

In which case, you should have both APs configured as AP-Bridge WDS mode, with each other's MAC addresses inserted in the settings as appropriate.

keycare did you get anywhere with this problem? I'm trying a very similar setup and can only see local clients, no internet access.