Testing my Erlang Blogger API ...

I'm stuck on this error message !

<<"org.xml.sax.SAXParseException: Content is not allowed in prolog.">>

I'm simply using this code:

request(AuthToken, Data) ->
        io:format("Sending: ~nContent-length: ~p~nBody:~n~s~n", [ size(Data), Data ]),
        Authorization = "GoogleLogin auth=" ++ AuthToken,
        Url = "http://www.blogger.com/feeds/19996386XX081936700/posts/default",
        case http:request(post,
                { Url,
                        [ { "Authorization", Authorization } ],
                        "application/atom+xml; charset=utf-8", Data},
                [ {timeout, 3000}, {sync, false} ],
                [ {body_format, binary} ]) of

                {ok, Result} ->
                        %io:format("Received: ~p~n", [Result]),
                        {_,_,Body} = Result,
                        Body;

                {error, Reason} ->
                        io:format("Error: ~p~n", [Reason])
        end.

And the resulting Body is always the error:

<<"org.xml.sax.SAXParseException: Content is not allowed in prolog.">>

Help Meeee !