Why does this https post request always return "404 Not Found"

FROM : an0
DATE : Sat Jun 21 15:43:14 2008

- (void) login
{
    NSString *userName = [[userNameField stringValue]

stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
    NSString *password = [[passwordField stringValue]

stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];

    NSURL *url = [NSURL URLWithString:@"https://secure.del.icio.us/login"];
    NSMutableURLRequest *urlRequest = [NSMutableURLRequest
                                      requestWithURL:url

cachePolicy:NSURLRequestReturnCacheDataElseLoad
                                      timeoutInterval:30];
    [urlRequest setHTTPMethod:@"POST"];
    NSString *body = [NSString stringWithFormat:
                      @"user_name=%@&"
                      @"password=%@",
                      userName, password];
    [urlRequest setHTTPBody:[body dataUsingEncoding:NSUTF8StringEncoding]];

    NSLog(@"request: %@\n%@\n%@",
          [urlRequest URL],
          [urlRequest HTTPMethod],
          [[[NSString alloc] initWithData:[urlRequest HTTPBody]
                                encoding:NSUTF8StringEncoding] autorelease]);

    NSData *urlData;
    NSURLResponse *response;
    NSError *error;
    urlData = [NSURLConnection sendSynchronousRequest:urlRequest
                                    returningResponse:&response
                                                error:&error];
    if (!urlData) {
        NSAlert *alert = [NSAlert alertWithError:error];
        [alert runModal];
        return;
    }

    // Parse the login result
    NSString *loginResult = [[[NSString alloc] initWithData:urlData

encoding:NSUTF8StringEncoding]
                            autorelease];
    NSLog(@"login result: %@", loginResult);
}

Is there anything special about https requests in Cocoa that I must
learn? Since I've verified that sending http requests in this manner
is perfectly OK, and accessing https://secure.del.icio.us/login in web
browsers goes well.
If anyone could tell me anything that I've missed here, I'll very much
appreciate that.