Hey Christian -- I'll post here, the info may help someone else too.
I uninstalled VE entirely (including manual search of any ensemble AU's or components) and re-installed after repairing permissions, rebooting, etc., as you recommended in the previous email. I reinstalled VE3, launched Logic, and Logic's AU Manager still shows version 2.0.0 of VE, although at least it validates this time. I don't know of any way to flush out or manually remove an AU from the AU Manager, so for now it still shows 2.0.0.
No WiFi involved: master is connected to the internet, and the second ethernet port connects to the slave. I have tried the ethernet cable on both ports of the slave, and it shows up in my NETWORK menu either way.
Network Utility gives me IP addresses for both ethernet ports. I have tried pinging the slave, and it responds/receives. I haven't changed any kind of network settings -- everything is as it was when I set up the new mac. Same with slave: I never changed network settings on it, as the ethernet port to the internet was the only use for ethernet on the now-slave machine.
So I think the next question is: where do I go, specifically, to assign an IP address (on each computer) and what settings do I need to change to get them to see each other?
Kerry