debugging ajax from a server

Hi, folks -

I'm debugging an HTML5 page that talks via ajax (JSON) to a ruby/Sinatra server. FIrefox 14.0.1 on Ubuntu 12.04LTS, server is on same machine but I'm addressing it via address:port rather than localhost:port.

When I use the debugger, the browser doesn't receive the response, although my server console shows it being sent. When I point the browser to the proper address:port, it does receive it, but I can't debug why the browser is rejecting my JSON.

I tried adding the CORS headers to my server response, no joy.

TIA! :D