When you login to the e-learning site, three different session cookies are set, these session cookies allow the system to remember who you are as you move around the site. If you are connected for a long time, or perhaps don't logout properly, these sessions can get out sync and one of the sessions may have expired. If this happens, you may get the screen shown below or you could get an "invalid token" message.
In either event, you need to logout of the site and close all web browsers. Be sure to close all types of browser you may have open. You may also need to re-boot your computer to ensure all sessions have been closed.
If you aren't in the system at a point where you can see the logout menu entry, close your web browser, start your browser again and navigate to elearnwithnca.co.uk. If the site thinks you are still logged in, log out as normal, and follow the above procedure.
In the unlikely event that this still doesn't resolve your problem, you may have to clear your web browser cache. This means deleting the history of what you've looked at online to ensure your browser downloads a fresh copy of the web pages. How you do this will depend on the browser being used - but an example for Internet Explorer can be found at http://windows.microsoft.com/en-gb/windows7/how-to-delete-your-browsing-history-in-internet-explorer-9