Yes, the first time I can load the page just fine. Then I go to the frequency dropdown and try to switch, and it redirects me to the URL without the port and the interface is not there of course. If I then add the port to the URL and manually load the page, the frequency and settings have been switched (which I guess means the form was submitted successfully, just the redirect doesn't work as it should).@BWR - Just to make sure I understand....it's correct the first time you select the page, but incorrect when you change the 'Frequency' selection?.
Something occured to me, the AP's which have a one to one port forwarding (TCP/8010 router -> TCP/8010 AP web interface) work correctly. It seems the problem occurs only when the forwarded port is not the same as the firmware web interface is run on.