If I publish a post manually with an image in it, the pinterest plugin works and posts it to my pinterest board automatically.
Also, the two errors that reference a missing file are correct- those two images are in fact missing. So ignore those two errors, but what do the others mean?
And finally, looking at the theme closer, I don't see any reference to featured images. Perhaps my theme doesn't even use featured images or is that a part of every Wordpress theme?
sorry, learning as I go along here...