I'm no expert, but here are my suggestions:

First, make sure that you have OpenSSL installed. http://www.webhostingtalk.com/showthread.php?t=929949

Second, check to see if there are any proxy settings that aren't getting carried through. http://forums.iis.net/p/1173290/1973896.aspx#1973896

Third, try implementing the headers and curl options from the last post here: http://bytes.com/topic/php/answers/734722-getting-php-login-somewhere-post-username-password-then-get-cookies