Error on redirect after logout

Hi
If a user is logged in and view their account through the link at the top 'my membership' they get the page as they should.

However, if they then use the link at the top menu to logout they then get the attached account page show.

If you then use that page to try to log back in it won't recognise the user name or password and the login link in the top menu does not show.

Completely lost why that is so?