iphone 3g can't find wifi??

[bigtomski]

I have a new iphone 3g which i've only had a couple of days so guess I might be asking a few questions over the next few weeks.......
The phone wont find any wifi signal when i'm at home.
Out and about it seems alright.
I have an imac at home with which I am connected to the internet using an airport extreme.
My airport can also see about 6 of my neighbours signals so why won't my phone find any of them???
I'm very puzzled by it.
And apologies in advance, I am a complete techno idiot.
Oh and I have turned the wifi connector to on on the phone.

[Tycho]

Is your network hidden?

You can specify the name of your network rather than the iPhone detecting it. Maybe that is the next thing to try.

[mcflurry]

Is mac address filtering enabled on your home network?