We posted an early build of MC26 on Friday and unfortunately it has had a lot of crashes. I apologize.
I think it's happening during import (at least). And perhaps thumbnailing.
It may be Windows Defender or registration of our controls during installation. We've had several install problems, as well.
We'll give it our top priority today and hope to get to the bottom of it.
Anything you've learned will be appreciated. Post here and include a log if possible. Logging has a topic on the wiki. After a crash, it is the Previouslog.txt that will have the useful information.