I downloaded a bunch of pictures from SmugMug. They were in the Download folder. I opened a few of them while they were in the download folder, double click on each and each came up in Preview. Then, I closed Preview, opened Download and clicked Cmd-A to select all. I opened iPhoto and dragged them into iPhoto. They look fine there and behave normally. Now, however, whenever Preview is opened, all those pics now located (100 of them!) in iPhoto open. How do I stop it? Thanks
The first thing I would try is going to System Preferences (on dock, or under the Apple logo in the Menu Bar), clicking "General", and checking "Close windows when quitting an application".