So Bonestar, I see your schwartz is as big as mine.  I see you tried to use system.net.webclient on a windows 2000 IIS5 machine to use DownloadData to access a site or webservice via HTTPS...  And you got the error above.  (or maybe it was contained inside a "The underlying connection was closed: Could not establish trust relationship for the SSL/TLS secure channel.")   So you googled around and found lots of people telling you to mess around with servicepointmanager to ignore all certificate errors.  You tried that right?  Still didn't work?  Did you spend all day trying to figure it out?  Well, let me ask you this:  when was the last time you ran Windows Update on that machine?  Quite a while I'm guessing.  It could quite possibly be that you need to download a "root certificate" update so that remote certificate is recognized.  Well, it worked for me at least.  Half a day lost, yes, but I'm gonna move on with my life.  I will start by pouring myself a glass of scotch.   On the rocks.