Fiddler is a tool for web debugging which essentially simulates a man in the middle attack. I'm using it to decrypt the SSL traffic coming from my computer. Although I can see everything coming from my browser I don't see any traffic coming from flash applications (a chat app).
I was thinking that maybe flash applications don't use the proxy server I set up in my browser in order to get Fiddler to intercept the traffic?
Oh, I can't use wireshark as it won't decrypt any SSL traffic unless I have the private key of the server, which I don't have.
Are you sure that the Flash applet is using HTTP or HTTPS? Flash can use direct socket connections, which do not run over HTTP or HTTPS, and thus are invisible to a proxy like Fiddler or Charles.
Fiddler can capture any HTTP or HTTPS traffic, regardless of its source, and typically captures Flash traffic with ease. Are you using Firefox, Chrome, or IE to run your applet?