NetworkManager-vpnc-0.6.4-3.fc7 Under NetworkManger/VPN Connections/Configure VPN.../<Connection name>/Edit the 'Apply' button is by default sensitive, and becomes insensitive when any settings are changed, unless the NAT keep alive settings (and only these settings) are changed, in which case the Apply button is again sensitive. As a result, unless you are only changing your NAT keepalive settings, you cannot edit connection settings.
Well, when you select 'Use NAT keepalive' or 'Use domain for authentication', the validation code actually checked the value you entered. That means that "Apply" will only become sensitive again *IF* you enter a sensible value in the field you just enabled... I can't seem to reproduce a case when apply is disabled when it should be on. Could you give me a specific scenario to reproduce ?
I can't reproduce now either, so I must have been having a bad day when I reported this. Closing.