If you're using the Modal Popup version, you'd need to make a minor edit to our files as we aren't using language strings for those 2 word. That will be fixed in the next release. To fix, edit the /modules/mod_sclogin/tmpl/login.php file and search for the words you're looking for on lines 13, 15, 19, and 21.
The Register page itself is a part of Joomla. You'd need to edit the com_users.ini language files to edit the text for those pages.
I hope that helps, but if you need anything else, just let me know.
Thanks,
Alex