Ubuntu Security :: Getting Errors "password You Use To Log In To Your Computer No Longer Matches"?

I have two things going on with my computer where I'm getting (error?) messages.

One is:

"The password you use to log in to your computer no longer matches that of your log in keyring."

This is in a window that pops up on my desktop after I log in and I have to enter my old password to get in the rest of the way.

I found this: url link and followed the path given in post #2. There, in the list, I find an entry named "uname@host" which shows my new/ changed host name. When I double click it and expand the "password" section at the bottom of the window I find that the password is indeed my new password, not the old one (you can tick box to "show password").

The other is, and I think this is connected:

When I use sudo in the terminal I get: "unable to resolve host"

I went to:

Code:
cd /etc; less hosts
and in the second line what I see is the old host name and not the new. I think that if I can correct this second thing, both will be resolved?? Or is that file even relevant to the situation??

If that is true, I want to make sure I go about it in the right way and not end up locking myself out of my own computer or something stupid like that.