Hi Daniel,
Normally when you see this message, it's because the browser is using an old version of the Explorer Online application from the browser cache, instead of checking for and getting the new version. That looks like Internet Explorer you're using - so go to the Internet Options dialog -> General tab -> Browsing history section, click Delete, and choose to delete at least temporary internet files.
I have had problems with IE, that even if I click the button to delete all browser cached files, it still hangs on to the old application. If you delete your browser cache and still get the same problem, my recommendation would be to go to the cache directly (Internet Options dialog -> General tab -> Browsing history section, click Settings, click View Files) and look for ExplorerOnline.xap and delete that file, then restart the browser. The latest copy of the application from the Esri website will then be downloaded.
Hope this helps