RESOLVED: Currently, you're not able to change your YouTube password. If you try to make a change to your password, you'll receive an "Authorization Error" message. We're working to correct this issue shortly and will update you when it's been fixed.
Update (6/14/2007, 5:53 PM PDT):
We've fixed the issue affecting users who tried to change their passwords. Everyone should now be able to change their passwords as usual.