I'm running Mac OS X 10.7.4 (Lion). I have the system preference that allows you to restore windows when quitting and re-opening apps turned OFF, as I really don't want a bunch of things popping up whenever I restart my computer or launch an application.
However, I don't know if this is the reason that CS5.5 and CS6 still try to open each other's open windows. On many occasions lately, I have to run 5.5 and 6 to switch between on different projects. Doesn't matter which one I launch first, but when I have a document active, and I launch the other application, it automatically presents a dialog: “Cannot open the document 'Macintosh HD:Users:username:folder:filename.indd'. You may not have permission of the document may be open already.” Of course, the document IS open already. But the other application automatically tries to access it.
I don't have this problem when I am running CS4 and CS5.5, or CS4 and CS6, which leads me to believe that it's an InDesign issue, not a system issue. But I don't know how to suppress the action. Any ideas? Thanks!