The strangest thing just happened. I was uploading attachments to a page when WordPress stopped storing the permalink in the database. The page_attachment_uris and rewrite_rules fields show that 4 attachments have been processed while the 5th image has not. Please see this link for reference: http://mfields.org/art/pieces/
I am using “Date and name based” permalinks.
Thanks in advance to anyone who knows what might be going on here,