Yep, I’ve just set up WPCR on a 4.0.1 installation and it all seemed to be working fine until I tried to updated existing comments from the admin area. It would not save anything by XHR and I’m unfortunately not proficient enough in WP development to figure out a fix.
I’m hoping that the new version that’s been promised will be along at some point, but as no news about this has been forthcoming since May 2014, it’s not looking good.