File/image upload via CCK and Nginx + FastCGI
Ok, turns out unbeknownst to me someone had added rules in the .htaccess file pointing image loading to another server, which, of course, did not have the created presets and thumbnails. Gah!

Another gotcha in this was the $base_url variable was set in settings.php to force Drupal to load a from a specific site, regardless of the one requested.

Hopefully this will help someone in the future.