This usually means that your scenario blueprint is over 5mb.
You can check the size by exporting your blueprint and checking the file size.
We've overcome this by 2 techniques.
1. Keeping usage of WF Search modules to a minimum. In our experience the WF Search module is the main culprit. We use the Custom API module to do searches.
2. Link Scenarios to each other so the workflow is spread over 2 or 3 scenarios.
Hope this helps.