I see this question hasn't been answered, and it's an old one, but maybe I can activate it again -
I'm having a similar problem. Out of nowhere, when i go to 3d window, there is nothing on the screen except a dark black line, that I can zoom in or out to, and click on. But nothing else.
This has probably happened only 5 or 6 times in the 8 years I've been working on AC - usually we will have to copy EVERYTHING and create a new file to paste into, and that "solves" the problem. But is there a better way?
Hope you can help!
Thanks,
Lara