POST seems to throw a 500 error code

[dev dev]

I just changed the following bookmark example code from PUT to POST and i
get an 500 status code using Simple Connector. What did i do wrong here? It
works fine if i change it back to use PUT instead of POST.

private static void addUser(String userName, String password,
            String fullName, String email) {
        Form form = new Form();
        form.add("user[password]", password);
        form.add("user[full_name]", fullName);
        form.add("user[email]", email);

        Response resp = new Client(Protocol.HTTP).*post(*
getUserUri(userName),
                form.getWebRepresentation());
        System.out.println(resp.getStatus());
    }

Thanks
dev