Months ago, Aral Balkan blogged about Service Capture not working with Flex Help and also gave a possible solution. (
link) His solution was to uncheck 'Modify IE Settings on Application Start/Stop". Unfortunately for me, I didn't want to uncheck that setting. I like that when I start Service Capture, it automatically sets up the proxy on open browser windows. Luckily, IE6 proxys traffic for "localhost" but doesn't for 127.0.0.1. Flex Help is initially setup to run from 127.0.0.1, hence, missing Service Capture. Therefore, going into Flex Builder -> Preferences -> Help -> Help Server and making the Host Name: "localhost" and the Server Port: "57266" allowed me to leave 'Modify IE Settings on Application Start/Stop" checked and still use Flex Help. I was happy...
Fast Forward to yesterday, when I decided to upgrade to IE 7. Oh No! My Flex Help is gone again...wassup with that?! Well it turns out, IE 7 no longer proxys "localhost" nor "127.0.0.1". So whats a fella to do? Hack! For some reason, "localhost." (notice the period) is proxy'ed. Changing the Host Name in Flex Help Server to "localhost.", a quick restart of Flex Builder, and all is well in my world once again!
Hope this helps someone!