Hello,
could you please let us know if ...
... you have been following the guide for setting up the PPTP-Connection posted in this forum.
... you have been able to successfully establish a PPTP connection before the error message appeared.
... you have changed your system (e.g. installed or changed your firewall, anti-virus software, etc.) before the error message appeared.
Please also post the settings you have entered and the operating system you are using to setup your connection.
Kind regards,
hideway2