iphone has wifi icon but not connected

I go into settings and connect to a network, the wifi icon appears on phone and shows in the settings that it is connected but when i try to use any app, i get a msg saying there is no internet connection. anyone know why this is? i have a 3g iphone.
thanks.

How are you connecting to the network? Does the network require a password? My iPod and Macbook have done this, and it was because the password for the network changed, so I had to change the password for it to remember.

Don't know why it said I was connected, but that's how I fixed it, maybe this is similar?

My ipod connection is refusing to work

hello, i have a problem, i got to my settings(on ipod), go on wifi and connect to our home network, it requires a password, of which i put in. then there is a tick beside the network and it shows full bars of network and at the top left, on the screen it shows there is network, but there is no tick beside it, when i go on safari it keeps on saying connecting and at the top left it shows there is signal but the icon keeps on rotating.I can access wifi when a password is not needed but, when a password is needed, as home it keeps on saying connecting. please help me