I'm not sure what would be wrong then. Can you go to the Joomla configuration area and enable "Debug System" setting. At the bottom of the page, it should show the language files that have been loaded on the page. Check if the socialprofiles_jomsocial.ini file was properly loaded.
Beyond that, try reverting the text string back to the default of:
PLG_SOCIALPROFILES_JOMSOCIAL_STATUS_UPDATE_HEADLINE="%s had a status update on Facebook"
Also, if you've updated that string and FTP'd it to the site, ensure that it was transferred as ASCII and not binary.
I hope that helps,
Alex