The exact project and tests will be attached internally. 

A logical steps copy/paste results in error upon playback:

'5/2/2014 2:25:06 PM' - Failure detected during execution. Details:
------------------------------------------------------------
'5/2/2014 2:25:06 PM' - System.ArgumentException: An item with the same key has already been added.
   at System.ThrowHelper.ThrowArgumentException(ExceptionResource resource)
   at System.Collections.Generic.Dictionary`2.Insert(TKey key, TValue value, Boolean add)
   at System.Collections.Generic.Dictionary`2.Add(TKey key, TValue value)
   at ArtOfTest.WebAii.Design.Execution.StepsTracer.RecurseBranches(LogicalBranchData bd, Int32& orderCounter)
   at ArtOfTest.WebAii.Design.Execution.StepsTracer.RecurseBranches(LogicalBranchData bd, Int32& orderCounter)
   at ArtOfTest.WebAii.Design.Execution.StepsTracer.Trace(Test test)
   at ArtOfTest.WebAii.Design.Execution.StepsTracer..ctor(Test test)
   at ArtOfTest.WebAii.Design.Execution.ExecutionEngine.InternalExecuteSteps(AutomationStepList stepList, TestResult testResult, Object codeBehindInstance, Boolean& stopExecution)
   at ArtOfTest.WebAii.Design.Execution.ExecutionEngine.InternalExecuteTestIteration(Object codeBehindInstance, Boolean isDataDriven)
   at ArtOfTest.WebAii.Design.Execution.ExecutionEngine.ExecuteDataDrivenTest(Test test, BaseWebAiiTest codeInstance)
   at ArtOfTest.WebAii.Design.Execution.ExecutionEngine.InternalExecuteTest(Test test, TestResult initializationResult)
   at ArtOfTest.WebAii.Design.Execution.TestExecuteProxy.ExecuteTest(ExecuteTestCommand command)

Customer confirmed deleting the stem and re-recording solved it for them:
"it was indeed the result of a copied and pasted logical step. Upon deleting that step and re-recording it on its own, the test now runs with no error"