If, in TFS 2010 Beta 1, you are encountering the error

TF31001: Cannot connect to Team Foundation Server at xxx.com. The server returned the following error: The ServicePointManager does not support proxies with the https scheme.

You can find an article I wrote that discusses how to resolve this issue on my "personal" blog, located here: http://blogs.msdn.com/ablock/archive/2009/05/20/for-tfs-2010-beta-1-resolving-tf31001-the-servicepointmanager-does-not-support-proxies-with-the-https-scheme.aspx#comments