I'll chime in here - I don't know if this is OP's issue, but I have experienced issues in the past with being able to clearly tell which languages in the list are selected, and/or the selected language settings saving properly.
I haven't played around with it in months, but at the time I thought maybe it was just my browser theme/system colour settings that were making it hard to tell exactly what was selected.
I agree with those who are saying that a list of possible languages with accompanying check boxes would be more intuitive than the current implementation.