Swf problem with reverse proxy

I have a nginx reverse proxy behind nginx web server.
I have a simple flash site, with swf embedded in html page.

I have a problem with this page, swf start loading but does not end.
If I point site directly to web server, swf work correctly.
Can you help me ?

My reverse proxy settings is these:

location / {
proxy_pass http://Backend;
proxy_http_version 1.1;
proxy_cache STATIC;
proxy_set_header Host $host;
proxy_set_header Accept-Encoding “”;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For
add_header X-Cache-Status $upstream_cache_status;
proxy_ignore_headers Cache-Control;
proxy_no_cache $http_pragma $http_authorization
$cookie_nocache $arg_nocache;
proxy_cache_bypass $http_pragma $http_authorization
$cookie_nocache $arg_nocache;
proxy_cache_valid 403 1m;
proxy_cache_use_stale error timeout invalid_header
http_500 http_502 http_503 http_504;
proxy_cache_methods HEAD GET;
proxy_cache_key $host$request_uri$cookie_user;


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