I was debugging with Fiddler without issue until today, when Symantec Endpoint Protection was enabled. Now, when I have both turned on, all browser traffic results in a 502 - connection failed.
Seems like something needs to be adjusted in Symantec so I can debug again. suggestions?
In Symantec Endpoint Protection, go to Network Threat Protection and check applications. In my case, Symantec was blocking any traffic through Firebug.