Can you tell us what strings aren't translated? Are you seeing the raw COM_JFBCONNECT_... string, or are you just seeing the string in English?
Please let us know any more information about what strings aren't being translated and we'll gladly investigate. The 6.4.0 release didn't have many string updates, but there were new plugins, like the Facebook Page Plugin, that simply don't have translations for some strings yet.
Thanks,
Alex