I tried Posser 11.1. It's the same issue. Slow material editor. Also if I a make a complete new installation without any additional scripts like DSON importer or so.

But it seems not everbody has this slow down issue with the newest windows updates. So the question is, what is the reason?

CPU? I use AMD CPU Threadripper.

Grafic card? i use Nividia GeForce GTX 1060 and 660ti

I'm more and more pessimistic to solve this issue. But I will try to install Poser on other PCs maybe I can find out what's the reason.