Normally this message comes when you are using eZee FrontDesk NextGen on network. If one of users have opened a room from one computer, and if you try to open the same room from another computer, this message will come. If you are sure, this is not the case, and the same room is not opened by any other user from any other computer. Please click on tools & utilities -> Network Locks. Select the room from the list and click on Delete button.