Suffering same problem.
Applied the fix (uploading the files and running the one on the forum's root).
Got this error on screen (running the archiver cron manually to see from the CP):
mySQL query error: SELECT archive_id FROM invision_forums_archive_posts WHERE archive_topic_id IN(1002644) AND archive_restored=0 ORDER BY archive_topic_id ASC, archive_id ASC LIMIT 0,250
But the topic we was watching, was unarchived.
Don't know what about that error.