Snow leopard changed my network configuration

I updated my MacBook to snow leopard successfully but when I restarted my computer it said my network configuration settings have changed. Now when I enter the wifi password the computer says it is incorrect and all other devices are having the same issue. The password is correct and I rebooted both the router and the computer. I went through network setup assistant with no luck . The computer picks up network but is unable to connect.

Any suggestions appreciated

MacBook, Mac OS X (10.5.8)