无法打开流：HTTP请求失败！ 需要HTTP / 1.1 407代理身份验证（ISA Server需要授权才能完成请求

I am strugling with this code:

$auth = base64_encode('domain\username:password');
$aContext = array(
    'http' => array(
        'proxy' => 'tcp://proxy:80',
        'request_fulluri' => true,
        'header' => "Proxy-Authorization: Basic $auth",
    ),
);
$cxContext = stream_context_create($aContext);

$sFile = file_get_contents("http://www.codecraft.gr", false, $cxContext);

echo $sFile;

i keep getting the following message

Warning: file_get_contents(http://www.codecraft.gr) [function.file-get-contents]: failed to open stream: HTTP request failed! HTTP/1.1 407 Proxy Authentication Required ( The ISA Server requires authorization to fulfill the request. Access to the Web P in C:\wamp\www\test17\tarantula.php on line 17

the thing is that myusername and password are correct, and i realy cant find something to help me with that ISA server :S any suggestions?

"A typical error that you will encounter is error 407 Proxy Authentication Required this means that the authentication has been denied because the user has no valid user account in the domain or that the password has been entered incorrectly." Microsoft ISA Troubleshooting guide. You should probably check if the user has the correct resource permissions then.