Just a note that the plugin Wordbooker by Steve Atty yields the following error when active together with your Attachments plugin:
Warning: substr() expects parameter 1 to be string, array given in /home/<mypath>/wp-content/plugins/wordbooker/wordbooker.php on line 1698
It can be replicated by trying to publish or republish a post to Facebook using Wordbooker. The error occurs when updating or publishing a post with a featured image.
Just wanted to let you know about this. Not sure who should provide a fix, you or the author of Wordbooker. I sent him notice as well.