Can't change email account

When I try to change my email address I get this error:

The password you have entered does not match your current one. Please press the back button, enter the correct details and try again. Don’t forget that the password is case sensitive. Forgotten your password? Click here!

I fill in the password field correctly. I know this because I copied the password from a text field to log in and then also paste it into the email field on the email/password change page.

How can I correct this?

From the forum front page:

Need to change your password or email address? Instructions are in our FAQ

(and that includes a link for FAQ)

From the FAQ:

For changing email address, use the CONTACT US link on the bottom of this or any page. For security reasons, the Login system doesn’t pass sensitive data back and forth to the Forum software.

I have found that link.
A question.
If you can’t change the email address, why is there a Change Your Password and Email page?

Because that is part of vBulletin, the software package used for the forums.
But the forums do not use vBulletin’s user administration. SUSE/openSUSE uses a central user administration with a centralized login. That is why you can use your username/password as well as on the forums as on e.g. Bugzilla.

I have sent an email through Contact Us.