@Kovid, While reviewing this error, I noticed that the metadata in every epub book in my library is screwed up. I did a epub to epub conversion on all of these with calibre version 0.8.20
Specifically the metadata screwed up in the epubs:
Title: contains random characters
Author: Unknown
Publisher: Hello World
Tags, ISBN and comments and Book Producer: calibre (0.8.20) [
http://calibre-ebook.com] are fine.
I never noticed because all of this info is fine when sent to device.
Update: If I set the Read metadata from file contents under Preferences - Adding books then all metadata is inserted in the book during conversion except for Publisher, that still says Hello World. If it is unchecked then I get garbage for Title and Author.
Maybe it has to do with the Quick preferences plugin?
Update: I removed quick preferences plugin, restarted, tried again. Any conversion with the Read metadata from file contents box unchecked inserts garbage for title and author.
Final Update: I wiped out my configuration settings and started fresh and everything works as expected.
The good news is the cover problem persists so that fix you created had nothing to do with my other errors.