Actually, Jim, according to the WD page and several of the YouTube pages, you should only still be encountering the problem if you're using your original YouTube password, as opposed to your Google Account/GMail password.
YouTube username + Google Account Password
Google Account username/email + Google Account Password
should be getting you in.
I know on my WDTV Live both ways work for me.
So, if neither of those is working for you, then this seems to be a separate (but similar) issue.
Several of the YouTube links point to rather useless information... the "I can't sign in" one basically only refers to the first time ever signing up/in... they basically tell you that the verification image is only valid for 2 minutes and you have to be faster in trying to sign in with your new account.
As far as I can see, once you sort through all their useless/worthless suggestions, the only option left is "Contact Us".