Jagadeesh,
Could you show us the Nodes on the graph? Also, strange questions but are you on a remote PC? I have noticed when I RDP into my machine that I loose the visibility of the graph.
Hi,
I’ve read somewhere in the bug section, that the newest release 0.81 is not supported by DirectX 10, and so the preview is not visible. I had the same problem and I moved back to the 0.8.
Hope I helped