Is this happening with one particular network or with all? Make sure iOS is updated on the device.
Reboot ipad by pressing and holding both the home and sleep/wake buttons at the same time until the apple logo appears on the screen, then let go. Then try to connect to network.
Go to settings, Toggle airplane mode on/off. Make sure bluetooth is off. Turn on wif (airplane mode off). Try to connect.
Reset Network Settings
Go to settings/general/reset/reset network settings. Then try to connect to network.
If its your home router, then reboot router by unplugging for 5-10min. (do this while you're resetting network settings).
If problem persists, then check for firmware updates on your router.(you check router manufacturer support website for downloads and instructions).
Wifi Settings greyed out or dim
Recommended wifi settings
Don't know about all networks, I haven't been in range of any others yet.
This is my home network, and it was - I believe - the OS update to 7 overnight that is a contributing factor. My laptop and my iPhone are both connected wirelessly to the router with the password.
I reset the iPad, reset the network settings again, toggled airplane on/off, turned off bluetooth.
When I go to connect to wi-fi, the error message I get is it is the wrong passcode - the same one I am using for both other devices.