Simple home setup, just the router no added APs. Two devices report connected but get no actual service, can't reach NET or LAN.

2 Humax PVRs, one connected via a WiFi dongle, the other by a WiFi bridge (Silvercrest) because I just can't get the other dongle to work.
HP Printer
Desktop PC with a WiFi card
Laptop (Fujitsu Lifebook)

For some reason the laptop appers to connect but reports no internet connection. After a disconnect and reconnect it works fine. The router was connected to internet all the time, so it seems like a WiFi problem but it could be some odd firewall or session thing?

One PVR connects fine via a "dongle".
The other one gets an IP address, reports that it is connected, but is unable to transfer data. It barely "sees" the LAN, occasionally recognising a media server.

What should I be looking for? I think I've tried swapping the dongles on the PVRs.

Well this morning I tried changing the channel bandwidth setting from 20/40 to 20, and so far everything is working including the RT3070 dongles in the PVRs. Evening now and still going strong.

Incidentally I'm using channel 11.

I also put the 3.6.8.7 firmware on but I doubt that made a difference as I understand the WiFi firmware stays the same revision as it was with 3.6.8.6.