I worked out what the problem was here. The issue is that after a WP eCommerce upgrade the server versions of the files user-log.php and edit-profile.php were updated. The lines that are modified when you install this plugin are subsequently lost and have to be re-added.
I’ve upgraded WP eCommerce a couple of times now and would really like to not have to do this each time we upgrade. Do you think future versions of this plugin could look at handling this differently somehow so we don’t have to insert any links manually?