Hi Peter, Can you please check if there are any active sessions listed in the Hosted control panel. If there are, end them by clicking the 'Log off user' option in the respective session then logout, ensure that you use the logout option in the top right corner.
Close your browser and then try again after 3-5 minutes.
You've cleared your browser cache which is good, in most cases this should have moved you past this error response.
If you're still having trouble after the above, please give us a buzz 1300 799 150 so we can get our technical support team on the case.