Seems like every preview build completely resets the networking components. So after a installing 10565 build, I had to uninstall / reinstall logmein hamachi to get it to work again.
Funny thing, the disk cleanup tool could not completely remove the windows.old folder created by the preview install. Apparently a hamachi driver was in use. I uninstalled hamachi again, did the disk cleanup, and re-installed. That worked.
Moral of the story, uninstall hamachi before installing a preview build. This may affect any other VPN or custom network apps you use.