Proxy returns 504 then blocks next connections

[abstein2]

The script is an ASPX script and, to my knowledge, it doesn't use sessions.
I don't control the script, but I can't duplicate the behavior when running
against the proxied server. It only occurs when going through the proxy. I
don't believe sessions are the issue.

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,240766,240842#msg-240842