graphviz (the renderer) is unfortunately prone to problems with very large graphs (which I'm guessing yours is). Is there any way to reduce the number of nodes you want to graph?

As an alternative, you may be able to save the graph in "canonical" format (that is, the actual dot source that would render the graph) and use ZGRViewer to visualize it - this program renders graphs as SVG and handles very large graphs better.

Upgrading may possibly help out, but I don't hold out hope that it will for sure fix your problem.