Same problem here, 5 to 30 seconds until disconnect.
$ apt-show-versions vpnc vpnc/feisty uptodate 0.4.0-2ubuntu1
$ uname -a Linux AngryButler68 2.6.20-13-386 #2 Sun Mar 25 00:18:53 UTC 2007 i686 GNU/Linux
Same problem here, 5 to 30 seconds until disconnect.
$ apt-show-versions vpnc
vpnc/feisty uptodate 0.4.0-2ubuntu1
$ uname -a
Linux AngryButler68 2.6.20-13-386 #2 Sun Mar 25 00:18:53 UTC 2007 i686 GNU/Linux