A. This is caused by either the RAS Connection Manager and Remote Access Server cannot be started or they are set to manual startup.
To fix just start the RAS Connection Manager and RAS and change the RAS Connection Manager startup to automatic using the Services control panel applet.
To test try to PING the PPTP server over the internet.
Another possibility (I spent forever trying to figure it out) when connecting to a pptp server with ms proxy 2.0. see the kb article here http://support.microsoft.com/support/kb/articles/Q176/9/24.ASP. In the packet filtering (ms proxy setting) you must add 'pptp receive' to get it to work.