[mrnuflo]

Ok, this is what I got:

Failed to initialize plugin: ISBNDB (1, 0, 0)
Failed to initialize plugin: <class 'calibre.ebooks.metadata.sources.isbndb.ISBNDB'>
Traceback (most recent call last):
  File "site-packages/calibre/customize/ui.py", line 519, in initialize_plugins
  File "site-packages/calibre/customize/ui.py", line 494, in initialize_plugin
InvalidPlugin: Initialization of plugin Traceback (most recent call last):
  File "site-packages/calibre/customize/ui.py", line 487, in initialize_plugin
  File "site-packages/calibre/ebooks/metadata/sources/isbndb.py", line 56, in __init__
  File "site-packages/calibre/utils/config.py", line 351, in __setitem__
  File "site-packages/calibre/utils/config.py", line 302, in commit
  File "site-packages/calibre/utils/lock.py", line 113, in __enter__
IOError: [Errno 13] Permission denied: u'/home/mrnuflo/.config/calibre/metadata_sources/ISBNDB.json'
 failed with traceback:
Traceback (most recent call last):
  File "site-packages/calibre/customize/ui.py", line 487, in initialize_plugin
  File "site-packages/calibre/ebooks/metadata/sources/isbndb.py", line 56, in __init__
  File "site-packages/calibre/utils/config.py", line 351, in __setitem__
  File "site-packages/calibre/utils/config.py", line 302, in commit
  File "site-packages/calibre/utils/lock.py", line 113, in __enter__
IOError: [Errno 13] Permission denied: u'/home/mrnuflo/.config/calibre/metadata_sources/ISBNDB.json'

Starting up...

So I simply closed it and then did "sudo chmod -R 755 /home/mrnuflo/.config/calibre" and it worked flawlessly. Thank you very much for your quick replies and help and for pointing me in the right direction! I love your app, good work!! I hope I'll become a programmer some day soon and give back to community too!!