Para aqueles que usam o Fiddler com IE 7 e não estão conseguindo capturar as requisições e respostas quando estão utilizando proxy, eis aqui uma dica que encontrei no próprio site da ferramenta:
IE7 and the .NET Framework are hardcoded not to send requests for Localhost through any proxies, and as a proxy, Fiddler cannot intercept such traffic.
The workaround is to use your machine name as the hostname instead of Localhost or 127.0.0.1. So, for instance, rather than hitting http://localhost:8081/mytestpage.aspx, instead visit http://machinename:8081/mytestpage.aspx. Alternatively, you can use http://localhost.:8081/mytestpage.aspx (note the trailing dot after localhost).
…Or, you could Customize your Rules file like so:
static function OnBeforeRequest(oSession:Fiddler.Session){
if (oSession.host.ToUpper() == “MYAPP”) { oSession.host = “127.0.0.1:8081”; }
}
…and then just hit http://myapp, which will act as an alias for 127.0.0.1:8081.