Let me get this right, so you have changed yr password and root password as well. In Mint 5 yr keyring usually authenticates when you log in if my understanding is correct. Therefore, because yr password id different now keyring will not automatically do this. I suggest this (BUT DO GO CHECK AROUND GOOGLE BEFORE YOU ATTEMPT THIS!) You may find that a good way to solve this is to delete the keyring file. When you try to connect using the network manager, keyring will ask you for a new password. (MAKE SURE IT IS THE SAME AS YR LOGIN PASSWORD!) Hence the authentication is taken care of at login. If you automatically log in without a password you need to switch this off as keyring would still ask you for a password. Paste this into a terminal and hit enter if you wish to delete the keyring file:
rm ~/.gnome2/keyrings/default.keyring
Can I also suggest that you may consider changing yr network manager to an application called 'wicd'. As far as I am aware this does not use keyring and I have used it with one or two not so good wireless hacks and it seemed more stable. It looks a little different but its not hard to figure. (NOTE AGAIN, HAVE A LITTLE BIT OF A GOOGLE BEFORE YOU TAKE THIS SUGGESTION IN ORDER TO GET A BALANCED VIEW, SOMEBODY ELSE MAY HAVE A BETTER IDEA) If you want to install 'wicd' then here is what to do. Open a terminal and paste in the following:
sudo gedit /etc/apt/sources.list
When the editor appears on yr desktop, copy in the following on a new line at the bottom:
deb
http://apt.wicd.net hardy extras
Now click save at the top and close the editor. Now type:
sudo wget -q
http://apt.wicd.net/wicd.gpg -O- | sudo apt-key add -
You will see yr system go off and get the key it needs to allow this repository to be used. When it has finished you will see an 'OK'. Now type:
aptitude update
You will now see all the Repositories verified. Now just install 'wicd'. Type:
aptitude install wicd
This will uninstall yr present network manager and install 'wicd'. To get it running just type wicd in a terminal. Cant remember if it will automatically start on reboot but if you check 'sessions' in 'preferences' it will tell you. If its not there just add it, its pretty straight forward. the command is:
wicd
Hope this helps.