thisoldman: Thanks, that solved it! I did have the line enabled in rc.conf, but had typed it as en_US.utf8 instead of en_US.UTF-8. A frustrating inconsistency... locales.gen lists it as en_US.UTF-8 (which I assume is why it should be listed that way in rc.conf), but when I run locale -a, it lists it as en_US.utf8. In any case, it appears to be working, now.
I have set the default language to Serbian and it hence the login page is now in Serbian Cyrillic.
However today I logged out and when Iogged in everything had reverted to US English.
I normally use LXDE but I logged into Gnome and that is now also in English.
I don't understand what I changed but keyboard crashed just before (which is why I logged out).