If you have one of the recent Nokia phones (N85, E71, N79, 5800, ...) and a recent Thomson / SpeedTouch / BT Home Hub router you may face the "No gateway reply" problem when using the WLAN. By trial and error, I found that this can be resolved by disabling WMM on the router via CLI. So it seems all of the phone's traffic is being QOSd away. Whose side the problem is on I don't know; they are both WiFi certified for WMM of course. An N95 (which doesn't have WMM support) is unaffected either way. Just thought I'd save someone who may come across this via Google the hours of pain I went through..
Someone actually did find this apparently judging by the comments. To access the CLI you normally use Telnet. Open a command prompt and type "Telnet 192.168.1.254" (if you changed the default IP... you probably don't need these instructions.) (Note: On Windows Vista you have to install Telnet client first, under Programs and Features in Control Panel). Enter your username and password. (For unbranded routers the default username is Administrator, case sensitive, with a blank password. Things may be different if your router is ISP branded.) Finally run these commands:
:wireless qos config mode=disabled :saveall