Some test are not executing while running through the Test Lists

Hi,

I have created couple of tests in Test Studio, those are executing fine when run in debug mode(Run from Test tab). If I add them into single test list then if we execute them from Test lists then those are not executing. I am using the Demo version of Test Studio(2012.2.920.0), is there any limitation for Demo version to execute the test?

The following exception produced in the log file

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'27/09/2012 11:59:31' - Using .Net Runtime version: '4.0.30319.269' for tests execution.
'27/09/2012 11:59:31' - Starting execution....
'27/09/2012 12:00:20' - Failure detected during execution. Details:
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'27/09/2012 12:00:20' - System.NullReferenceException: Object reference not set to an instance of an object.
   at ArtOfTest.WebAii.Design.Execution.ExecutionEngine.InitializeWpf(ExecutionEngineCreateParams initParams)
   at ArtOfTest.WebAii.Design.Execution.TestExecuteProxy.CreateAndInitializeEngine(Test test, ExecutionEngineCreateParams cp)
   at ArtOfTest.WebAii.Design.Execution.TestExecuteProxy.ExecuteTest(ExecuteTestCommand command)
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'27/09/2012 12:00:21' - Test completed!

Regards,
Nathan