Node.JS and SSL certificate

I was running my node.js app with autosigned certificates. That was working pretty well, except I was forced to accept certificate every time I opened chrome. Then I bought an SSL certificate (actually a wildcard) from Gandi. And I'm currently trying to put the certificates in my nodeapp.

var http = require( "http" );
var https = require( "https" );
var fs = require( "fs" );
var url  = require( "url" );
var crypto = require("crypto");

function start(route,handle) {
    function onRequest(request, response) {
            var pathname = url.parse(request.url).pathname;
            //console.log("Requete recue pour le chemin "+pathname+".");
            route(handle, pathname, response, request);
    }

    var options = {
            key: fs.readFileSync('privatekey.pem').toString(),
            cert: fs.readFileSync('certificate.pem').toString()
    };

    var app = https.createServer(options,onRequest);
    var io = require('socket.io').listen( app );
    io.set('log level', 1);
    app.listen( 8080 );
    io.sockets.on('connection', function (socket) {


    });
    console.log("Server's launching");
}

With the signed certificate, server's launching and running but everytime I call

https://mydomain/ or https://mydomain:8080/ 

I get a

Erreur 107 (net::ERR_SSL_PROTOCOL_ERROR) : Erreur de protocole SSL

Any idea ? How can I have more infos regarding the error ? Any help much appreciated...