Synapse can't download file

Question

I'm making a DLL (for GameMaker 8) with Lazarus. I have a function:

function Download(URL: PChar; FileName: PChar):double; cdecl;
var
  HTTPClient : THTTPSend;
begin
  HTTPClient := THTTPSend.Create;
  try
    if(Ping(URL, 4000) <> 4000) then
    begin
      if HTTPClient.HTTPMethod('GET', URL) then
      begin
        HTTPClient.Document.SaveToFile(FileName);
        if HTTPClient.ResultCode = 200 then Result := 1 else Result := 2;
      end
      else Result := 0;
    end
    else Result := 0;
  finally
    HTTPClient.Free;
  end;
end; 

And the Ping function is:

function Ping(ip:PChar; ttl:double):double; cdecl;
var PingSend: TPINGSend; PingBool: boolean;
begin
  PingSend := TPINGSend.Create;
  try
    PingSend.Timeout := round(ttl);
    PingBool := PingSend.Ping(ip);
    if PingBool = True then Result := PingSend.PingTime else Result := PingSend.Timeout;
  finally
    PingSend.Free;
  end;
end;   

In the URL I provide, for example, "http://www.google.co.in/images/nav_logo4.png" (no quotes). In the FileName I provide "D:\logo.png", a file that doesn't exist. No matter what I try, function always returns 0 (which means HTTPMethod didn't work) and doesn't save the file (though, it worked for some time before, but maybe I modified something crucial). The DLL's function is defined correctly in GameMaker, it freezes if providing an unreachable URL (Ping = 4000).

I'm kinda new to DLLs, Synapse and Lazarus. Is there something I'm doing wrong?