Rails app may be crashing passenger, not sure how to debug?

My app generates some image data on the fly and sends it back to the browser with send_data some_huge_blob, :type => 'image/png'. This works well enough in development mode, but in production with nginx/passenger in the mix it appears as if sometimes passenger just crashes. Here is the debug output in my nginx log

[ pid=596 thr=140172782794496 file=ext/common/ApplicationPool/Pool.h:1162 time=2011-07-25 23:15:14.965 ]: Exception occurred while connecting to checked out process 1428: Cannot connect to Unix socket '/tmp/passenger.1.0.589/generation-0/backends/ruby.kJRjXYuZteKoogZIufN8a2cDPdpbIlYmIr1hh3G9UV7GhKDB4pqZ5y0jR': Connection refused (111)
[ pid=596 thr=140172782794496 file=ext/common/ApplicationPool/Pool.h:685 time=2011-07-25 23:15:14.965 ]: Detaching process 1428
[ pid=596 thr=140172782794496 file=ext/common/ApplicationPool/../Process.h:138 time=2011-07-25 23:15:14.969 ]: Application process 1428 (0x2676ee0): destroyed.
[ pid=1405 thr=70178806733240 file=abstract_request_handler.rb:466 time=2011-07-25 23:15:14.982 ]: Accepting new request on main socket
2011/07/25 23:15:16 [error] 642#0: *96 upstream prematurely closed connection while reading response header from upstream, client: 173.8.216.57, server: app.somedomain.com, request: "GET /projects/4e2dee4c106a821bf2000008/revisions/1/assets/Layout2.psd/preview HTTP/1.1", upstream: "passenger:unix:/pa开发者_高级运维ssenger_helper_server:", host: "app.somedomain.com"

Note that there is nothing in my production.log file that indicates the request even makes it to the app!

Any ideas? Or ideas as to how to debug this further? The connection refused bit is interesting...

For what it's worth, this is an Ubuntu image on a micro instance in AWS.