I was using an old version of Komento. I have now upgraded to the latest version 2.0.5
This was a major release upgrade 1 to 2 so I performed the database upgrade.
The site was working under the release 1 versions of the component.
Now whenever I have Komento enabled everyone gets the message "you don't have permission to view or post comments"
I can enable other comment (Facebook or Disqus) in Easyblog and they work ok.
Martin