Specific step results drill-down throws the exception (available in the application log):
Situation: Unhandled exception!
Outer Exception Type: System.NullReferenceException
Message: Object reference not set to an instance of an object.
HRESULT: 0x80004003 (Official ID (if app.) = E_POINTER, Error Bit = FAILED, Facility = FACILITY_NULL, Code = 16387)
Call Stack:
at ArtOfTest.WebAii.Design.UI.StepDebug.StepDebugFailureUI.Initialize(AutomationStep step, AutomationStepResult result, TestResult testresult, String resultsPath)
at ArtOfTest.WebAii.Design.UI.TestResultsPane.ShowStepFailureDetailsDialog(AutomationStep step, AutomationStepResult stepResult, TestResult testResult)
at ArtOfTest.WebAii.Design.UI.TestResultsPane.DrillDownStepResult(StepResultItem item, Boolean updateLastBreadCrumbTitle)
at ArtOfTest.WebAii.Design.UI.TestResultsPane.stepResultsGrid_MouseDoubleClick(Object sender, MouseButtonEventArgs e)
http://screencast.com/t/Qv9SsedwEay