Comment 3 for bug 1002254

More details:

All of the above was with a VPN connection configured within network-manager-gnome. So, there is incompatibility in the profile that it saves. If you don't want to deal with the incompatibility, don't display it.

I added a new VPNC configuration using KDE's interface to do so. With this one, I consistently get the dialog prompting me to enter the password when I click on it (or at least I did until I clicked on the old 'xxx' one, after which neither works again.) However, in syslog there are yet more errors:

May 21 07:36:40 fridge vpnagent[1443]: Function: tableCallbackHandler File: RouteMgr.cpp Line: 1694 Invoked Function: recv Return Code: 11 (0x0000000B) Description: unknown
May 21 07:36:52 fridge sudo: pam_ecryptfs: pam_sm_authenticate: /home/rfirmin is already mounted
May 21 07:37:49 fridge vpnagent[1443]: Function: tableCallbackHandler File: RouteMgr.cpp Line: 1694 Invoked Function: recv Return Code: 11 (0x0000000B) Description: unknown
May 21 07:37:52 fridge NetworkManager[1250]: <info> Starting VPN service 'vpnc'...
May 21 07:37:52 fridge NetworkManager[1250]: <info> VPN service 'vpnc' started (org.freedesktop.NetworkManager.vpnc), PID 3395
May 21 07:37:52 fridge NetworkManager[1250]: <info> VPN service 'vpnc' appeared; activating connections
May 21 07:38:10 fridge NetworkManager[1250]: <info> VPN plugin state changed: starting (3)
May 21 07:38:10 fridge NetworkManager[1250]: <info> VPN connection 'xxx2' (Connect) reply received.
May 21 07:38:10 fridge NetworkManager[1250]: SCPlugin-Ifupdown: devices added (path: /sys/devices/virtual/net/tun0, iface: tun0)
May 21 07:38:10 fridge NetworkManager[1250]: SCPlugin-Ifupdown: device added (path: /sys/devices/virtual/net/tun0, iface: tun0): no ifupdown configuration found.
May 21 07:38:10 fridge avahi-daemon[1272]: Withdrawing workstation service for tun0.
May 21 07:38:10 fridge NetworkManager[1250]: SCPlugin-Ifupdown: devices removed (path: /sys/devices/virtual/net/tun0, iface: tun0)
May 21 07:38:10 fridge NetworkManager[1250]: <warn> VPN plugin failed: 0
May 21 07:38:10 fridge NetworkManager[1250]: <info> VPN plugin state changed: stopped (6)
May 21 07:38:10 fridge NetworkManager[1250]: <info> VPN plugin state change reason: 10
May 21 07:38:10 fridge NetworkManager[1250]: <warn> error disconnecting VPN: Could not process the request because no VPN connection was active.
May 21 07:38:10 fridge NetworkManager[1250]: <info> Policy set 'Wired connection 1' (eth0) as default for IPv4 routing and DNS.
May 21 07:38:15 fridge NetworkManager[1250]: <info> VPN service 'vpnc' disappeared
May 21 07:38:19 fridge vpnagent[1443]: Function: tableCallbackHandler File: RouteMgr.cpp Line: 1694 Invoked Function: recv Return Code: 11 (0x0000000B) Description: unknown