Thanks for your comments.
I got an info in another forum, that the gpu doesn't make a big difference in rendering anything with Vue, besides OpenGL.
If I switch to wireframe mode option in the settings, Vue is becoming much more stable. As I could see, Vue 8 doesn't has a wireframe mode any more. So I'm afraid of instability. Vue 8 seems to need OpenGL for many features. But it isn't profitable to buy a big graphic card just for this.
What do you say about this?

Greetings
Roland