Hi,
Thanks for sharing this issue. I've been quickly able to recreate it in exactly the manner you described.
The issue also appears outside of NCrunch, when performing the same actions with any other test runner. This suggests the issue is something with SpecFlow or the CLR itself. My understanding is that the ExecutionEngineException is generally caused by problems outside managed code.
Perhaps you could raise this issue with SpecFlow and see if they have a solution for it?
Cheers,
Remco