Not sure if it's just me but every time I upgrade Jomsocial I have to add the "COM_USERS_LOGIN_REMEMBER_ME" to the language-file. (Like COM_USERS_LOGIN_REMEMBER_ME="Remember me")
It's an easy fix but it would be easier if it was there from the start :). Is this a bug or is it just me?
that language Constant belong to Joomla user component. the value location at /language/en-GB/en-GB.com_users.ini (maybe the Constant missing from here)
you can make override at joomla language manager or put it at en-GB.com_users.ini, so it will not always missing.
