Hi, first kill network manager:
Then restart it, telling it not to daemonize
# killall NetworkManager NetworkManagerDispatcher
This will print messages to the terminal. I am having what appears to be the same problem as you, mine comes down to this error:
# NetworkManager --no-daemon
** (process:16186): WARNING **: <WARNING> nm_vpnc_dbus_init (): Could not acquire the dbus service. dbus_bus_request_name() says: 'Connection ":1.8037" is not allowed to own the service "org.freedesktop.NetworkManager.vpnc" due to security policies in the configuration file'