Amazon currently has some issues with S3 and it's causing intermittent issues with the deploy of graphs, running of graphs, connecting to S3 from a graph, and showing the project model. We apologize for the inconvenience and we are closely monitoring the situation. You can also monitor it here: http://status.aws.amazon.com/ . We are going to keep you updated on the resolution.
We are happy to tell you that the issue is now solved and the service is operating normally! Thank you for your patience.