I've frequently been bit by failures restarting my vpn on my Mac. The connection may appear to start up in Shimo (the menu icon will change) but it looks like vpnc can't connect.
Looking at the log, we see the connection gets stuck
ERROR: can't send packet: Can't assign requested address
This has plagued me for a while, and my only fix has been to restart the machine. I hate restarting my machine. So I finally made time to dig in and find a better solution