I tried the Grindmachine CM together with Cubase Pro 8 64-bit on Win7 64-bit. I used the 64-bit version of Grindmachine CM. It loads fine and works fine, but when I start moving the plugin to a different track or try to replace it with another plugin, Cubase crashes immediately, Windows message: "This application as stopped working". This happens for medium sized projects, 10-20 other plugins (only Cubases own plugs), 20-40 tracks.
What is worse: when this happens it is not enough to restart Cubase, if you do that it behaves strange, saving takes about four times as long as before. You have to reboot the Win7 as well, then everything works ok, as long as you do not load Grindmachine CM again, of course.