One of my users tried to register with the facebook button and he reported that the user was not created and he was stuck in the homepage.
I checked the error log and this is the info.
Date User Area Type Info
28/03/2014 15:44 Unknown create_new_wp_user_from_fb exception Cannot create a user with punctuation characters (#$!%&:wink: in login name.
The user e-mail and facebook profile has nothing different then any other profile, and also does not have any character.