I just got a new mac, and have accidentally set up something weird with my applications. I can only ever have one application showing on the desktop although I have a few programs open. As soon as I click on another application on the dock the current window open will hide and the new one will show. It's nothing to do with spaces or anything, I haven't got that turned on. The only way that I can have different application windows open is if I hold 'command' and 'tab', and select a different application.