Channel.Call.Failed occurring sporadically when proxy settings are configured in the browser

Question

I have a BlazeDS service making calls through a SecureAMFChannel as part of a Flex 4 client -> Java server application hosted with tomcat. I'm seeing a strange issue in which the service calls cause a seemingly random NetConnection.Call.Failed (faultCode = Channel.Call.Failed) fault when there are any proxy settings set in the browser. We do not utilize a proxy.

For example, when running through Firefox, if the "Automatically detect proxy settings" option is checked in the Advanced network connection settings, it will sporadically throw the NetConnection.Call.Failed fault. Setting the option to "No Proxy" will cause the faults to go away.

For Internet explorer, a group policy setting must be disabled, as outlined in this article, before the sporadic connection faults will go away.

There are no server-side message lines in any of the tomcat logs. Using firebug with AMFExplorer, it seems like the issue is occurring purely client-side, within the flex swf app.

Pinging wpad results in a "Ping request could not find host wpad".

I have tried moving to the non-secure AMF channel, as well as both HTTP and HTTPS, with no luck (the issue still occurs). This is confusing me to no end. If there is anything I should post, let me know.

UPDATE:
I've tracked a lot of the sporadic issues to the AJP timeout settings, as outlined in the issue here. Unfortunately, the fault still occurs, although seemingly less often.

Answer 1

Much of the issue was traced from this similar stack question:

NetConnection.Call.Failed happening sporadically in Flex3/Tomcat/BlazeDS/Spring

Unfortunately, while it did alleviate some of the issue, there were still sporadic faults. I traced the rest of the faults to a bug in firefox that occurs when the Auto-detect proxy is enabled, causing it to lose a few headers, as specified here:

https://bugzilla.mozilla.org/show_bug.cgi?id=669759

This firefox bug was fixed around September 2012. Updating to the latest version of firefox, or a version after that date will fix the issue.