I'm encountering a problem and hope it's just my own stupidity that's causing this.
Every time I try to add a new book (tried with .lit, .epub and others) I receive this warning.
The books are fresh and have never been added to the library. If I choose OK 2 entries are created. One contains the original ebook, the other a ZIP file. This only started happening today, and I already have some 100+ books in the library that imported without any such errors.
I'm running Mac OS X 10.5.6 and Calibre 0.4.139.
Thanks in advance for any advice.