The Drush Make utility downloads modules from ftp.drupal.org during the build - but the ftp.drupal.org site is currently down, which means Drush Make won't work (and so our continuous integration has ground to a halt).
There's a fix for general Drush usage here: http://contrib.linalis.com/content/continuer-dutiliser-drush-quand-ftpdrupalorg-est-down
That fix changes the download url to use drupal.org (which is working) instead of ftp.drupal.org (which isn't).
Unfortunately Drush Make uses it's own download functions, so this doesn't help.. Here's my (very similar) hack to get the Drush Make downloads working..
Change line 367 in drush_make.drush.inc to the following:
'url' => str_replace('ftp.', '', $release['file']),
(The file should be somewhere like /usr/share/drush/commands/drush_make)
And don't forget to remove the hack when ftp.drupal.org comes back..