If you're getting the error message "Security problem. Please try reloading the page. We cannot verify your account credentials. Please verify your account information, then sign in again." then your Google Analytics session is no longer active.
This can happen if you leave the web page idle for too long, or if you log into a different google account in a different tab in the same browser. When you log into a Google account using the same browser, any other Google account sessions are automatically timed out.
Solution
Pressing the 'Close' button over and over won't change anything. You have to refresh your browser by pressing the 'F5' key. You may have to re-log into your Google Analytics account.