This is really weird. I recently upgraded from OS X 10.8.5 to 10.9.2, and from Aperture 3.4.2 (whatever was most current under Mountain Lion) to Aperture 3.5.1. Today I tried dragging a photo from my Aperture library to the Flickr icon under “Shared,” and the drag is possible, but the photo is not uploaded.

I disabled, then reenabled my Flickr account in Aperture, and now uploading works via contextual menu “Share > Flickr”. But it still doesn’t work to drag files to the “Flickr” icon in the sidebar; in fact, Aperture seems to interpret the drag as one to the Photostream icon (i.e. I see the sync icon appear briefly next to it).

Any idea as to what could be wrong? I’ve also tried deleting and reinstalling the app.

(followup) I have determined that this problem arises immediately after my Aperture Library is upgraded from the 3.4.5 format to the 3.5.1 format. I opened a backup (dating from before I upgraded from Mountain Lion to Mavericks) of my Aperture Library with Aperture 3.4.5 –> no problem. I opened the same backup with Aperture 3.5.1, allowed Aperture to convert the library, and then dragging photos to the Flickr icon cause the Photostream sync to begin and do not upload to Flickr.

If I create a new library, then the problem doesn’t occur, so the problem must be somewhat specific to my library. I’ve tried repairing permissions and repairing the database, to no avail. Again, the problem didn’t exist before the conversion to the Aperture 3.5.1 format.