I'm getting the following set of errors in a project, that previously worked fine, from NUnit for VS when I try to run either individual or all of the tests in a given solution. Error loading C:\Path to Application\Application\Application.ApplicationTests\bin\Debug\Application.ApplicationTests.dll: The method or operation is not implemented. Error loading C:\Path to Application\Application\Application.FileDetectorTests\bin\Debug\FileDetectorTests.dll: The method or operation is not implemented. Error loading C:\Path to Application\Application\Application.PresentationTests\bin\Debug\Application.PresentationTests.dll: The method or operation is not implemented. Error loading C:\Path to Application\Application\Application.DomainTests\bin\Debug\Application.DomainTests.dll: The method or operation is not implemented. I've verified that each project is setup with the appropriate ProjectTypeGuids for a test project in the Project file. I've tried uninstalling / reinstalling NUnit for VS, but have had no luck. Does anyone have any advice as to how I might start troubleshooting this? If I open each individual test project outside of the main solution (that includes all projects, by the way,) and save it as it's own solution, they run just fine. Nothing of note has changed since this stopped working. Thanks! Ian