Xperia X10 :: It Won't Connect WiFi To Home Network

I still have to wait for full-functionality on my X10 when the service provider gets updated to a new contract in a few weeks.However, I cant get it to connect to my home wi-fi network.It recognises the network and remembers it. The Network Key is good. Ive tried both with and without 'data traffic enabled', and of course the phones Wi-Fi is turned on- Ive tried that both through the main screen and through the Wi-Fi Settings screen.I got a shock bill last week because the phone was using dial-up connection instead of Wi-Fi without me realising it!Also, how can I ensure it chooses unsecured or 'FreeZones' when on the move over dial-up? I want to be able to use the Navigation function, but worry about the phone being connected too much, even with the internet bundle I am subscribing to.