php-cgi/nginx returns http/0.9

When I visit content type management page and try to delete a file field or a content type contains a file field, I get a page without any css or js. I can click submit but it doesn't work (it doesn't update or delete that field).

When I proxy the page to apache, the problem doesn't show up.

I use nginx-for-drupal conf at github. I didn't add or change anything.

I disabled all the third party modules and the problem still exist.

I run nginx 0.9.2, PHP 5.3.2-1ubuntu4.7 with Suhosin-Patch (cli) (built: Jan 12 2011 18:36:08), latest version of d7. [ php installed using apt on ubuntu]

I can't reproduce this every time, but I can consistently reproduce most of the time on all the sites running on the same server.

By looking at the http header of the page in question, I see nginx gives http/0.9 header. This is strange. According to nginx docs, this means the proxied backend responses with http/0.9. (which means php-cgi?)

Currently my solution is running these sites on apache. But I want to use nginx, the conf is much clearer and more elegant.

Attached is the http header:

http://example.com/admin/structure/types/manage/video-mysite/fields