To be fair, I was up and running, just in a very basic video mode. And I could have reverted to the built-in video controller, though I suspect some of the games wouldn't run if I did that.
I don't know what the games don't like about antiviral software, but I think it has to do with how high-end graphics-intensive games try to kick as much of the OS out of the way as possible to run faster. The AV SW doesn't like that, as it looks like malware behavior. There's probably a way to tune the AV SW so it ignores particular programs, e.g. these games. I've never had to bother looking into this sort of thing, myself -- the last "game" I played was (I think) "3 in Three" on Mac OS 7. Although now that I think about it, I think I played a few IF games since then, on my Palm Pilot and iLiad.
I'm definitely going to need one of those adapters. Thanks for the link, slayda!