If you have logged in successfully and still see the message "you must be logged in to post a comment" then please "refresh" the page you are currently on.
You will find the option to refresh typically under the "View" drop-down list menu on your browser.
Microsoft Internet Explorer: –> View –> Refresh or F5
Mozilla Firefox: –> View –> Reload or Ctrl+R
Opera: –> Right-Mouse-Click –> Reload or Ctrl+R
This issue only occurs when a certain cache is applied to make the pages load faster on this site. Often, in the past, this has been deactivated (due to incompatibilities that made the site function incorrectly) and has recently been activated again.