Why can't I unzip this file with photo?

I downloaded my Flicker albums awhile ago, and they were saved as zip files. I just tried opening several of these files that are zipped, and got a message saying "Unable to expand in to Dropbox. I don't have these files in Dropbox, although they used to be. I have them in my Download folder. I also checked all my permissions, in Dropbox as well, and I don't see why this error would come up.