Calibre me da error al intentar añadir libros para convertirlos

Me Aparece este mensaje:

calibre 2.22 is frozen: True is64bit: False
Windows-8-6.2.9200 Windows ('32bit', 'WindowsPE')
32bit process running on 64bit windows
('Windows', '8', '6.2.9200')
Python 2.7.9
Windows: ('8', '6.2.9200', '', 'Multiprocessor Free')
Traceback (most recent call last):
File "site-packages\calibre\gui2\add.py", line 116, in tick
File "site-packages\calibre\gui2\add.py", line 204, in monitor_scan
UnicodeDecodeError: 'utf8' codec can't decode byte 0xe1 in position 429: invalid continuation byte