Return path module (working edition)
Due to poor reading of the issue queue AND not looking for the HEAD release, I (accidentally?) coded the fix to this myself. But actually both head and the official release are broken in different ways, so here's Agaric's service to the community.
Presumably the official version at http://drupal.org/project/returnpath will be working soon (version 5.x-1.1 does NOT), but until then here's a working download.
Correct path to file download: http://www.agaricdesign.com/sites/default/files/returnpath-mod.zip