Here is a post on how to change keyring password on Ubuntu http://www.greenhughes.com/content/how-change-default-keyring-password-u...

It works on Ubuntu 10.4 too. The only trick on me is that, in order to change the default keyring password of a desktop user, I had to first change the user to administrator, then login to that user, change keyring pwd. After that, I can change the user back to a regular "desktop" user.