I've got WiFi turned on in the settings, and ask before connect turned off. My iPhone 3G should see several WiFi networks, but it lists none. It also does not list my own network, which my computers see just fine. It has worked earlier but stopped working recently (possibly because of or at the same time of other trouble (which a restore solved)). The iPhone is not jailbroken.

The SSID is not hidden, uses WPA2. It also finds no WiFi networks when I'm at a friend's house. His iPhone 2G sees several WiFi networks, including his own.

When I use the manual entry method, specifying my home SSID and the proper WPA2 passkey, then click join, the iPhone says couldn't find that network. Same at my friend's place, with his SSID and passkey.

I've just backed up my iPhone, then restored it, to see if refreshing the firmware would help. It didn't change anything.

Is my iPhone broken? How can I fix this?