Sorry for not following up, I'm writing a custom module to do what we need (since it is pretty specialized, and is going to use a Perl script to handle the large file uploads).

Anyways to troubleshoot your white screen problem, put this into the top of your index.php:

error_reporting(E_ALL);
ini_set('display_errors', TRUE);
ini_set('display_startup_errors', TRUE);

That'll show you any fatal errors (which Drupal chokes on). It's helped me tons.