error description: could not parse proxy url

Question

I have seen the answers to the existing two questions on this topic but it has not helped. And the problem still persists so I am re-posting this question.

Here is my code

$(function(){
SE.init({ 
    clientId: <id>, 
    key: '<key>', 
    channelUrl: 'http://example.com/stack/',
    complete: function(data) { 
        $('#login-button')
            .removeAttr('disabled');
    }});

$('#login-button').click(function() {
    SE.authenticate({
        success: function(data) { 
            alert(
                'User Authorized with account id = ' + 
                data.networkUsers[0].account_id + ', got access token = ' + 
                data.accessToken
            ); 
        },
        error: function(data) { 
            alert('An error occurred:\n' + data.errorName + '\n' + data.errorMessage); 
        },
        networkUsers: true
    });
});
});

Even the javascript SDK code shows the same problem. The error shows up irrespective of whether I am signed in or not.