Having a similar problem with MPPE. Applying the network-manager - 0.7~~svn20081018t105859-0ubuntu2 proposed patch from Bug #290468 appears to have fixed the dialogue box, but the VPN still fails. I can connect through the console using the PPTP plugin directly using the instructions from this page:
For whatever reason Network manager still has issues with the PPTP plugin and/or with MPPE security settings. I attempted a fix from PPA but it made no difference.
Having a similar problem with MPPE. Applying the network-manager - 0.7~~svn2008101 8t105859- 0ubuntu2 proposed patch from Bug #290468 appears to have fixed the dialogue box, but the VPN still fails. I can connect through the console using the PPTP plugin directly using the instructions from this page:
http:// pptpclient. sourceforge. net/howto- debian. phtml
For whatever reason Network manager still has issues with the PPTP plugin and/or with MPPE security settings. I attempted a fix from PPA but it made no difference.