Jo, I've put up a new version with some rudimentary logging, can you give it a shot and let me know what errors you see?
v0.5.2
- Install 0.5.2 and restart firefox
- Open up the Tools -> Error Console and clear it out
- try to create a book, make sure 'add to calibre' and 'launch calibre' are enabled.
Let me know if you see any errors in the Error Console window. There's probably one from trying to delete the working directory. I've seen that but haven't worked out what the cause is.
Edit to Add: I also add the --duplicates option when adding to the calibredb to force adding a new book even if there is a duplicate author/title in the current db.