I would suspect your languages table is not correct in some manner maybe an early beta?. Looking at the default code this is what I see.
Code:
Content visible to verified customers only.
The language insert in phrase.php matches that. My suggestion is you delete your phrases and languages table and then run upgrade.php
Your comment on phrases.php your message above shows it says phrase.php and thats an easy thing I can change the wording to say phrases.php easy.
As far as a few versions not sure what you mean by versions as this code is all new in 3.1 so it has not been around for a few versions.