runnetworksIf the firewall blocks the vnc port, it's either coming from your internal network or that machine. Did you check the "only accept connections from the local machine" checkbox? That is checked by default on the kasey install, but sometimes gets disabled.
I have seen invalid protocol errors a couple of times, but wasn't concerned about it. Maybe I should have been. All of my firewalls block vnc inbound by default as well.