错误99 - 在last.fm php API调用中拒绝权限

I'm making a call to retrieve a user's latest tracks using the last.fm PHP api library. It works perfectly when I run it on my local webserver (localhost), but when I run it on a remote server it sends back an error code of 99, saying that permission has been denied.

Here is my code:

static function readRecentTracks() {
    $authVars['apiKey'] = '#########';
    $auth = new lastfmApiAuth('setsession', $authVars);
    $apiClass = new lastfmApi();
    $packageClass = $apiClass->getPackage($auth, 'user');
    $method_vars = array(
        'user' => 'liquidus219',
        'limit' => 25
    );

    if ($tracks = $packageClass->getRecentTracks($method_vars)) {
        echo json_encode($tracks);
    } else {
        echo '<b>Error '.$packageClass->error['code'].' - </b><i>'.$packageClass->error['desc'].'</i>';
    }
}

You can see the code in action at http://liquidus219.freehostia.com/api/?q=readRecentTracks

UPDATE: I have checked/changed the application URL to no effect.

UPDATE: I have gone through the code for the last.fm PHP api, no sign of an error 99 defined anywhere.

I found out in the end that my hosting provider was blocking the call.