Hi Charlie,

You're right. I do have 3.5 since I'm on Windows 7, and it shows up under Windows features instead of the usual Add/Remove Programs. So that mystery is solved. :-)

I don't see a way to choose the framework in NUnit 2.6.2 GUI. I see Test Loader->Runtime Selection and there is a single checkbox "Select default runtime version based on target framework of test assembly". It is checked.

I do have "Reload before each test run" checked, so your analysis of the debug log is correct.

From nunit-agent_7248.log:
InternalTrace: Initializing at level Verbose
17:00:16.976 Info  [ 1] NUnitTestAgent: Agent process 7248 starting
17:00:16.976 Info  [ 1] NUnitTestAgent: Running under version 4.0.30319.18063, Net 4.5
17:00:16.976 Info  [ 1] NUnitTestAgent: Adding Services
17:00:16.976 Debug [ 1] ServiceManager: Added SettingsService
17:00:16.976 Debug [ 1] ServiceManager: Added ProjectService
17:00:16.976 Debug [ 1] ServiceManager: Added DomainManager
17:00:16.976 Debug [ 1] ServiceManager: Added AddinRegistry
17:00:16.976 Debug [ 1] ServiceManager: Added AddinManager
17:00:16.976 Info  [ 1] NUnitTestAgent: Initializing Services
17:00:16.992 Info  [ 1] ServiceManager: Initializing SettingsService
17:00:16.992 Info  [ 1] ServiceManager: Initializing ProjectService
17:00:16.992 Info  [ 1] ServiceManager: Initializing DomainManager
17:00:16.992 Info  [ 1] ServiceManager: Initializing AddinRegistry
17:00:16.992 Info  [ 1] ServiceManager: Initializing AddinManager
17:00:16.992 Debug [ 1] ServiceManager: Request for service IAddinRegistry satisfied by AddinRegistry
17:00:16.992 Info  [ 1] NUnitTestAgent: Connecting to TestAgency at tcp://127.0.0.1:64997/TestAgency
17:00:16.992 Info  [ 1] NUnitTestAgent: Starting RemoteTestAgent
17:00:16.992 Info  [ 1] RemoteTestAgent: Agent starting
17:00:17.007 Debug [ 1] RemoteTestAgent: Registered with TestAgency
17:00:17.007 Debug [ 1] NUnitTestAgent: Waiting for stopSignal
17:00:17.070 Info  [ 5] TestDomain: Loading TestHPC.dll
17:00:17.070 Debug [ 5] ServiceManager: Request for service DomainManager satisfied by DomainManager
17:00:17.070 Debug [ 5] ServiceManager: Request for service ProjectService satisfied by ProjectService
17:00:17.085 Debug [ 5] ServiceManager: Request for service ISettings satisfied by SettingsService
17:00:17.085 Info  [ 5] DomainManager: Creating AppDomain test-domain-TestHPC.dll
17:00:17.241 Info  [ 5] TestDomain: Loading tests in AppDomain, see test-domain-TestHPC.dll_7248.log
17:00:17.663 Info  [ 5] TestDomain: BeginRun in AppDomain test-domain-TestHPC.dll
17:14:20.717 Info  [13] TestDomain: Unloading
17:14:20.717 Info  [13] TestDomain: Stopping DomainAgent
17:14:20.717 Info  [13] TestDomain: Unloading AppDomain test-domain-TestHPC.dll
17:14:20.717 Info  [13] DomainManager: Unloading AppDomain test-domain-TestHPC.dll
17:14:20.733 Info  [13] RemoteTestAgent: Stopping
17:14:20.733 Debug [ 1] NUnitTestAgent: Stop signal received
17:14:20.733 Info  [ 1] NUnitTestAgent: Unregistering Channel
17:14:20.733 Info  [ 1] NUnitTestAgent: Stopping all services
17:14:20.748 Info  [ 1] ServiceManager: Stopping AddinManager
17:14:20.748 Info  [ 1] ServiceManager: Stopping AddinRegistry
17:14:20.748 Info  [ 1] ServiceManager: Stopping DomainManager
17:14:20.748 Info  [ 1] ServiceManager: Stopping ProjectService
17:14:20.748 Info  [ 1] ServiceManager: Stopping SettingsService
17:14:20.748 Info  [ 1] NUnitTestAgent: Agent process 7248 exiting