Silly me!
I'm working on this managed application that's doing some remoting. The app's got all sorts of heterogenous channels being mixed and matched....at one point I was getting an error with this text: "Tcp channel protocol violation: expecting preamble."
I found some very interesting causes for this exception except of course in my particular scenario. Turns out that I was trying to make a tcp:// request to a https:// server channel. Whoops! Anyway, I figured I'd share since I didn't see any other info out there for this error with this cause.