This error is being raised by the build step responsible for registering this assembly for COM interop. When UAC is enabled on your machine, the build process needs to be granted administrator privileges in order to perform the registration.

I'm not entirely sure why Visual Studio lets you build this project without you running it as administrator, but my guess would be that the assembly has already been registered before at its normal build path, so probably the build step is being skipped in this case.

COM registration of assemblies under NCrunch workspaces is probably not something you want to do as part of an NCrunch build. There's an easy way to suppress this behaviour when working with NCrunch. Open up the project file and look for the property:

<RegisterForComInterop>true</RegisterForComInterop>

.. And replace it with:

<RegisterForComInterop Condition="$(NCrunch) != '1'">true</RegisterForComInterop>

This will allow the COM registration to happen for any normal build, but it will be skipped when working with NCrunch. This will remove the need to run VS as administrator, while also improving your build performance.

Great! Thanks for confirming. Enjoy the product :)

This means we have now discovered the next problem :)

Are you able to get a debugger into the tests that are hanging? What can you tell me about these tests?