I am using LabVIEW 8.2 and TestStand 3.5. I use the default Operatore Interface (full featured) provided by NI. The TestExec.exe does not close properly when I exit the application. Everytime the process is running in windows. I had to use Windows Task Manager to kill the TestExec.exe manaully.
There could be some execution still running. Check the execution list and see whether it is " Executions[0]". If not there could be some there is some execution still running.
I found the reason, actually in station options. debug options / warning dialogs are enabled for memory leak. which was showing a warning dialog when engine shuts down. I disabled it, it works.