Rails receiving the wrong body

I have a problem with the following code that calls a remote service with a POST request and receives JSON data:

[..]
var options = {
    host:   REMOTE_HOST,
    port:   REMOTE_HOST_POST,
    path:   REMOTE_PATH,
    method: 'POST'
};

var req = http.request(options, function(res) {
    res.setEncoding('utf8');
    res.on('data', function (data) {
        // handles OK
    });
});

req.on('error', function(e) {
    // handles KO
});

req.write('user=myname&password=mypassword');
req.end();
[..]

It works ok on my OSX machine, but when I try it on a co-worker Windows computer, the data sent to the server is wrong and I don't know what could be causing the problem. The remote application doesn't receive user=myname&password=mypassword as expected but:

35\r\nuser=myname&password=mypassword

What could be the cause of this? thanks

EDIT

Seems like the problem is not Node.js Further investigation evidences that also my OSX box gives the same error when calling the dev server, while it works ok in production. Seems like a Rails problem. I'