Airport error: incorrect password

[shorinn]

I have a Macbook 1.83 GHz Intel Core 2 Duo running Mac OS X10.4.11 which, up until a week ago, always connected flawlessly to the internet via our home wireless network. Now, I am able to connect, but I must create a new connection via the "other" box under the Airport icon every time that the computer goes to sleep or starts up. Although our network is shown under the airport icon, when the computer wakes up from sleep and searches for a network, it states "none of your trusted networks can be found". When airport tries to connect to our home network without me selecting "other" and creating a new connection, I get the message, "the password that you have entered is incorrect." This process occurs with any encrypted network, not just our home network.
My wife has a Dell Laptop that connects every time without problems.
I have a Netgear router using WPA encryption.
I have updated the firmware on the router, reset the password on the router, changed the encryption from WPA to WPA2.
I have cleared my Keychain numerous times on the Mac, and deleted then repopulated my Trusted Networks list.
In summary, I am able to connect when I create a new connection every time, but I am unable to connect by selecting an available network from the Airport icon without getting either "password... is incorrect" or "unable to connect to the network", despite the password being correct.