As can be seen in the attached images, books transferred by Calibre to my PRS-600 Sony Reader Touch Edition receive odd characters, largely Chinese, replacing the last couple letters of a book title or author name. This occurs on both the internal storage, and on the 8GB MicroSD card I'm using (with a MicroSD to SD converter).

Why would this happen, and what can I do to stop it?

I do not have a solution for you but I would like to add that I have the same problem with my PRS-600.

It is only in the title and author. Never in the text of the books themselves.

Happened to me once - after I strayed and gave in to the dark side of eBooks :o.

it's a known problem with setting metadata in certain types of PDF files. There's an open ticket about it in the calibre bug tracker.