After changing your login password, you may also want to change your keyring password. Changing your keyring password in Ubuntu is easily done. All you need to use is a little program called seahorse which is probably already installed on your computer.

To run it from the Gnome menu, find it at Applications -> Accessories -> Passwords and Encryption Keys

If seahorse is not installed on your system, you can install it by running the following command in a terminal:

sudo apt-get install seahorse

When you run the program, you'll see in the main window some text that says "Passwords: login". Well, all you have to do is right click on that text that says "Passwords: login" and from the right click menu that comes up, just click on "Change Password". From there, you just enter your old keyring password, then enter your new keyring password twice.

Once you've done that, you may need to log out and log back in again for your new keyring password to take effect.