After testing a WP installation with all kinds of testposts and several extra custom fields (keys) for use with postdata, I deleted all posts to give the owner of the site the chance to begin with all new posts. But now I noticed that the three extra custom fields I added are also gone and I can't add new ones.
When I try to add a custom field to an existing post it says
An unidentified error has occurred.
and when I write a new post I can add new fields, but the 'key' fields stay empty nonetheless. And after saving the post and opening it again, those three (empty) fields are gone again.
My database table wp_postmeta shows _edit_lock and _edit_last in several places. What happened and how can I correct it?