I've just been bitten by the same bug while trying to send messages from Ruby to a JMS implementation via the StompConnect gateway. I believe that the Ruby client shouldn't add any headers that aren't required by the protocol, and the AFAICT protocol doesn't require content-type.
There's a patch on RubyForge that allows ruby clients to tell the driver to not send the content-type header, which would work OK for me:
http://rubyforge.org/tracker/index.php?func=detail&aid=16967&group_id=1010&atid=3983What do the Ruby client developers think of this patch?
Thanks,
Toby