Do you see any schedules that failed to complete? They'd still show a status of "running"....
Have you tried restarting the Admin console?
It seems like the admin console goes "deaf" after awhile and we have to relaunch the console before we get it to respond again.
Thanks a lot your reply. I already restarted the admin console by clicking the "Start Admin Console" Button under https://[host]:1600. However this did not change anything. I was still not able to close the databases. I see the list with the databases, I can select one and can chose "close" from the menu, but the status of the databse remains "normal".
I am not quite sure about the schedules. There are backup schedules with the status "Access denied" (or the like, my console is in German.) Could it help to deactivate all the scheduled tasks?