I have just run into a situation where 3 of my sites are getting the error "Access denied! The server is currently out of SESSION CALs". All the sites have only 1 SESSION CAL in their license. The error will come up when navigating from one dashboard to another. If you select the dashboard again, it will display fine. The sites are running QV server 8.50.6231.5. I was also able to recreate this on one of our in-house systems. It would seem that the session cal hasn't been released when going to another dashboard. Is there a setting that can be adjusted that would eliminate this error?
You may set the session timeout in both document (Settings menu, Document Properties, Server) and Enterprise Management Console, under System, your QlikView server, Documents and Performance tabs in the right pane.