Encountered some odd drupal+apache2+nginx interaction bug today. Basically, "Transfer-encoding: chunked" was done on the content twice if drupal 404'd. Doesn't seem to trigger outside of drupal, IIRC. Don't know exactly which fault was it, but:
described it and nginx author Igor Sysoev gave a patch to fix it. His own development version of nginx doesn't seem to have that patch incoorperated, but the patch made the bug go away.
Win. I had hacked nginx .deb for Ubuntu Hardy amd64 at my informal work site.