Thanks for posting. This is most likely due to a different in the processor architecture of the hosting process. There is a lack of standardisation around X86/X64 between test runners - please read this documentation page for more information. You can confirm whether the issue is X86/X64 based by comparing IntPtr.Size between test runs.
It seems as though your test project has been designed to only work with an X64 architecture.
So to me it makes sense for you to change the processor architecture in the build configuration for this project to X64. In this way, there's no way the project can be loaded in an X86 architecture. NCrunch will detect this and will run as X64.
Can you describe the problem you're experiencing right now? Does changing the architecture as you have done not have any effect on the process? (i.e. is it still launching as X86?)