colszowka/xbmc-client — pull request #5 by cornet (2012-11-24 01:35:02+00:00)
Title: Content-Type header is required for v5 of the API

From http://wiki.xbmc.org/index.php?title=JSON-RPC_API

FUTURE FRODO FEATURE:
Starting with Frodo nightly builds it is mandatory to set the HTTP header field Content-Type: application/json