Comment 4 for bug 163623

My wireless interface (eth0) was configured using network-manager, with the wired interface (eth0) is disabled. But I also get the "no currently active network device, won't activate VPN" error in syslog whenever I try activating VPN through network-manager.

A work-around seems to be to rename the interfaces so that eth0 is the active connection (in my case, the wireless). See: http://ubuntuforums.org/showthread.php?t=601671

But a better solution would be to make the network-manager use the routing table in determining which interface to use for the vpn.