I had a similar issue a few days ago. When I opened any dynamo 2.0 graph, Dynamo crashed.
I changed the dynamo build from Dynamo Revit 2.1.0.6086 to Dynamo Revit 2.1.0.5565 and that seems to solve my problem.
But I can not be sure that the dynamo version was the only cause of the problem.
I do not know if it’s the solution to your problem. It could also be a new package installation or an addin that interferes with dynamo or something else.