The language key names have changed in JFBConnect v3.2.2. These changes were meant to make the Joomla 1.5 and Joomla 1.6 strings the same for easy development and migration. For instance, the previous key of "Login Using Facebook" is now "COM_JFBCONNECT_LOGIN_USING_FACEBOOK". This is causing both of the problems above:
1. sedes - I found that the es-ES.com_jfbconnect.ini file that we released has a bug in it. The first key should be COM_JFBCONNECT_LOGIN_USING_FACEBOOK, but is COM_JFBCONNECT_LOGIN USING FACEBOOK. (missing some of the underscores). Can you updated this key and see if it fixes your issue?
2. Niccolò - we do not include an Italian com_jfbconnect.ini file in the installation. I logged into your
test.alkemica.net and there was already a file there (that I am assuming you made yourself?) but it had the older language keys. I renamed the file you had and added a new language file for 3.2.2. This fixed the problem on your test site. If you're interested, feel free to contribute the file back to us once you've finalized the language strings - we'll include it in the next release.