No changes made when updating existing posts/pages

Strangely… all of a sudden excisting pages and posts didn’t seem to update. WP said: Post saved, but then just showed the post without the changes. Most posts and pages were changed before; naturally absolutely no problem at all.

No error messages, no 404’s and no changes to any excisting post or page (grmbbl).

Then I added a new post and I was able to change en re-edit that new post only. I decided (for some reason) to run the plugin WP-optimize (which I had run without any problems before) and afterwards all was well again. What happened?? I have trouble trusting my database after this event..