When I click the download link from admin/reports/updates, I get a 404 message.

The problem is this:

http://ftp.drupal.org/files/projects/apachesolr_biblio-6.x-1.x-dev.tar.gz

It should be changed to:

http://drupal.org/project/apachesolr_biblio

In other words, the scheme (http://ftp), the path (projects) and the filename (apachesolr_biblio-6.x-1.x-dev.tar.gz) are all wrong.