httpwebrequest ssl fails

i'm controlling code, ask given url:

private stationary twine getwebrequestcontent(string url)
{
  twine sid = string.empty;

  httpwebrequest req = (httpwebrequest)httpwebrequest.create(url);
  req.keepalive = false;

  controlling (httpwebresponse res = (httpwebresponse)req.getresponse())
  {
    controlling (streamreader sr = new streamreader(res.getresponsestream()))
    {
      sid = sr.readtoend().trim();
    }
  }

  relapse sid;
}

i'm controlling exam stickyness work bucket balancer, 3 servers behind it. have stationary htm record called sid.htm, where server's server id written.

for url's http works fine. nonetheless https doesn't work. i exception:

the ask aborted: emanate ssl/tls secure channel.

at moment, i have wholly 2 servers behind wlb the possess open ip behind firewall. https requests works glorious i strike stand-alone server - nonetheless i strike wlb i above error.

one thing: method switch between dispute unparalleled server, wlb i hosts file. dns annals domain points unparalleled server during moment. i put record hosts record strike wlb. shouldn't causing problems...

my question: ssl credentials/certificates does httpwebrequest use? uses 40 bit des 56 bit des, that's reason, since those noxious wlb. nonetheless those certificates haven't used browsers given ie3 netscape 1 2.