Flickr sets not synchronizing with Aperture
I have been using Aperture successfully to upload to my Flickr account for some time, but today I have been unable to upload images to a set. Curiously however, I can upload to my Photostream directly. I can use Flickr to move those items into a set, but in Aperture, I will never see those items in the set, no matter how many times I choose to "synchronize".
The feel of synchronization seems weird now. The publish or synchronize buttons induce a quick spin of the status icon, as if they are doing their job, then almost instantly stop, but nothing has happened. Like I say though, I can share to my photostream just fine though, so there doesn't seem to be any overall problem with the account connection.
I'm considering removing the Flickr account connection from my Aperture preferences, then remaking it, but I'm loathe to try that. I don't want to loose all of Aperture's existing knowledge of how the items in my Flickr sets correspond to items in my library, and I suspect I would lose that if I deleted the Flickr link.
Any suggestion of a less drastic solution before I try this would be welcome.
Extra points for fair disclosure or irrelevant extra information:
I had to reinstall Aperture 3.4.1 a month or so ago, after a failed update. Apple techs told me to do so after Aperture would crash when starting, from an apparently not uncommon bug with the installer. Although Facebook synchronization is working fine, I believe this is the first time since that I have tried uploading to Flickr.
Aperture 3, OS X Mountain Lion (10.8.2)