While checking Google Webmaster Tools I discovered that all the links to my library (bottom of right sidebar) had failed.
The Now Reading plugin that I use for my library requires Permalinks to be set to ‘Custom’ for it to work. Permalinks are what allow this post to have a URL like . In this case combined with the rewrite in the plugin they allow my library to appear to to be here http://blog.ijhedges.com/library/ .
I can only guess one of the WordPress updates reset this. I’ll have to keep an eye on it in the future after upgrades.