I’ve experienced this issue several times now with Nuendo 6.5.XX 64bits (I’m currently on 6.5.30) on OSX 10.8.5, working on a 5.1 session.
Some automation parameters won’t play after a while (open and close the session a few times). Even worse, I can’t edit it anymore, it becomes grey. I can still see my entry points but that’s it. And of course, it’s not read anymore.
The 2 parameters involved : Surround Panner V5 signal width and Surround Panner V5 Front-Rear Pan. You’ll see better with the screenshot I’ve attached. Do you have any clue ?