Have you opened the Keychain Access program in your Utilities Folder? Look for the file with the name of your wireless network and you can delete it, reconnect to your network, and re-enter the password. That may work if the keychain item is not working.
Or, go to System Preferences and under the Network Pane, select AirPort, click Advanced, and double-click on your network name. This may prompt you with a message asking about your keychain and after accepting, it will bring up another window with your network name, your security type, and the password. Try changing the password there as well. Let us know how that turns out.
-BMF
I changed the password on my regular D Link wifi router and all computers accepted the change including my MacBook, except for the macmini. I can I change the passward in the mini to match the new password on the network?
Thanks

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