Missing argument 3 for wp_set_post_series()

Hi!
HUGE problem here. I’m part of a team using a wordpress website, and for whatever reason, another member of the team had the wonderful idea to update the plugin to the latest (2.4.6) version, without checking the changelog first. Of course, now, everything is broken. I managed to reupload and activate the 2.4.5 version, but it remains broken.
I’m getting this error everytime I try to post an article and give it a part in a series :

Warning: Missing argument 3 for wp_set_post_series() in /mydomainhere/www/wp-content/plugins/organize-series/orgSeries-taxonomy.php on line 483

Warning: Cannot modify header information – headers already sent by (output started at /mydomainhere/www/wp-content/plugins/organize-series/orgSeries-taxonomy.php:483) in /homez.490/espacesc/www/wp-includes/pluggable.php on line 876

When I’m not trying to post an article, just to write it (and not having done anything series-related then), I’m getting this one:
Warning: Missing argument 3 for wp_set_post_series() in /mydomain/www/wp-content/plugins/organize-series/orgSeries-taxonomy.php on line 483
(but not the headers stuff, which seems logical since I haven’t posted anything)

What’s happening? How can I fix this?
(And no, I don’t want to upgrade to the latest version of wordpress right now, I have absolutely no time at the moment to deal with the various broken plugins till the beginning of January, I’m just looking to patch things until I can sit down in front of my computer and spend the next few hours dealing with unavoidable problems.)

Thanks!

http://wordpress.org/plugins/organize-series/