Hello fludyfield,
Here are a few suggestions that you might want to try -
Try to manually enter the wifi configuration settings (Name of your wifi, password) on your phone and then see if it'll connect.
In the settings you might want to select "Forget this Network" and then try reconnecting.
Make sure that your on the most current/recent firmware update for your device. It's possible that there maybe a WiFi bug on the firmware version that your using.
Also check and make sure that the routers settings are correct.
First try and unplug the router for like 10-15 seconds and then plug it back in to reset the router.
Even try setting or changing it from WPA to WEP and vise/versa and see if that helps.
You can try and manually switching the wireless mode to 802.11b , if it's on automatic.
Also make sure that your SSID isn't hidden... you need it to broadcast the SSID.
Hope this helps and good luck! :thumbup: