Error adding books to Calibre

Hi,
Sorry for my very bad english.
I have Calibre library shared with dropbox on two computers (Mac and Windows 7).
After upgrade to version 0.8.68 (latest), I can't add books from Calibre on Mac (on Windows works fine).
This is the error:

***
calibre, version 0.8.68
ADVERTENCIA: Fallo leyendo metadatos: Fallo leyendo metadatos de:

7810-164.mobi
Traceback (most recent call last):
File "site-packages/calibre/gui2/add.py", line 127, in start
File "site-packages/calibre/gui2/add.py", line 217, in add
File "site-packages/calibre/library/database2.py", line 3335, in create_book_entry
File "site-packages/calibre/library/sqlite.py", line 314, in run
DatabaseException: user-defined function raised exception
RemoteTraceback (most recent call last):
File "site-packages/calibre/library/sqlite.py", line 271, in run
OperationalError: user-defined function raised exception
***

Any help?

Thanks for your interesting.
Diego.