bug 51 may possibly be fixed, and as such it is not a known bug anymore:

51.Kevin Reed's reported problem with a proxy when doing CONNECT and it
  wants NTLM and close the connection to the initial CONNECT response:
  http://curl.haxx.se/bug/view.cgi?id=1879375

docs/KNOWN_BUGS

@@ -8,10 +8,6 @@ may have been fixed since this was written!
   SSL-negoatiated:
   http://curl.haxx.se/mail/lib-2008-01/0277.html
 
-51.Kevin Reed's reported problem with a proxy when doing CONNECT and it
-  wants NTLM and close the connection to the initial CONNECT response:
-  http://curl.haxx.se/bug/view.cgi?id=1879375
-
 49. If using --retry and the transfer timeouts (possibly due to using -m or
   -y/-Y) the next attempt doesn't resume the transfer properly from what was
   downloaded in the previous attempt but will truncate and restart at the