Formidable upload file don't trigger

Development and test environment:

• Windows 8 64bit
• node version installed 0.10.5
• npm version 1.2.18
• express framework
• formidable module used for file uploading
• Firefox and Internet Explorer browsers

HTML code:

<form id="caricaMasterImg" method="post" enctype="multipart/form-data" action="/image/upload"> 
    <input type="file" id="masterImg" name="masterImg" value="Sfoglia" accept="image/*"/>
    <input type="submit" value="carica" id="submitLoadImg" />
</form>

app.js code:

var image = require('./route/image');
app.post('/image/upload', image.upload);

routes/image.js code:

exports.upload = function(req, res){
    var form = new formidable.IncomingForm();
    form.uploadDir =  path.join(__dirname, 'tmp');
    console.log('Upload directory is: '+form.uploadDir);
    fs.exists(form.uploadDir, function (exists) {
        console.log('is an existing directory? '+exists);
    });
    form.parse(req, function(err, fields, files) {
        console.log(fields);
        console.log(files);
    }); 
};

The issue:

When submit button is clicked I expect to see the file logged with console.log(files) instruction. Log writes:

Upload directory is: C:\Liber-I\app\FileSystemManager\routes\tmp is an existing directory? true

No more log is written on application console for several minutes. I test the case of no-file submission and it seems it is acting the same! It is a too weired behaviour to be a nodejs problem, where am I doing wrong?