Javascript submit form & RJS

I’m using javascript to submit a form using the onclick and getting a
response using RJS. Everything works fine except for the returned
response
is coming back as text no matter what I do. I am attempting to
explicitly
set the Content-Type header and I tried using the :type param to render
but
nothing seems to work. Any suggestions?

Env:

OSX
Lighttpd
Rails Edge

Thanks!