Hello, I am having this exact same problem - our security team can see the firewall blocking Graphite because it is not using our proxy server.
I notice that starting in Graphite 1.3 it now supports proxy servers: http://docs.icenium.com/release-notes/v1-3#http-proxy-support
But I don't see any place to configure the proxy server. I just see a mostly blank application frame - only the buttons that link to the documentation, forums, etc. are available. No settings, no right-click, nothing else.