I have recently finally got round to working on a flex project using the all new 64 bit coldfusion beast on my mac. Had a slight problem with the ol’ connectivity between Flex and CF though so I whipped out my standard test application and that didnt work either….? Now this got weird cos when I did the standard flex2gateway url check it worked fine, the only thing that was different here in my approach was the new Flex Project builder screen for ColdFusion. My error output showed trouble with http://localhost/QueryCFC/flex2gateway, hold on a minute?!? So a little google work and the solution was found here @ CFWTF, specifically this part:

…as far as I can tell, that magic url always needs to be http://yourdomain.com/flex2gateway, anything you put in this field will cause that call to fail, and in your flex app you’ll get something like Channel.Connect.Failed error NetConnection.Call.Failed: HTTP: Status 405:

Ahhhhh, so the solution was to LEAVE THE CONTEXT ROOT FIELD BLANK!