Ketarin download error when trying to pass POST vars in URL

[dtgm]

An exception occurred during a WebClient request. (http://api.thebrain.com/?a=doDirectDownload&id=70)

Triggered not by my code, but for reference, here is how I am getting the 64-bit file (may need to be fixed):

  string savePath64 = Path.Combine(varWorkdir, saveFileName64);
  System.Net.WebClient webClient = new System.Net.WebClient();
  webClient.DownloadFile(varChecksum64File, savePath64);

[dtgm]

{url:encode} / {url:decode} do not seem to help