Well, Rat, that leaves only two options: The solution was either a) installing all 3 updates, or b) re-validating the Poser software, because that's the only two new things I did.

You never know, Smith Micro may have accidentally left out an earlier update feature in Service Pack 3 - which incidentally for some strange reason is called SP3 but downloads and installs as Service Pack 4. I've never been able to find an installable Service Pack 3!