Launching MicroStation using Windows Task Scheduler

I have a DOS batch file that launches MicroStation, runs a script using the -s switch.  The script will run a MVBA which performs some CAD functions then exits MicroStation.  The functions performed do not impact this question, so I have not included them here.

Test 1 - double click the .bat file, MicroStation launches, the script and vba run and software exits.  Success. 

Test 2 - I setup a task in Windows Task Scheduler to run the DOS batch file.  Under security options I select 'Run only when user is logged on'.  I run the task.  Success.

Test 3 - I change the Security option in the Windows Task to the option 'Run whether the user is logged on or not'.  I run the task, which fails to complete.  MicroStation is launched, confirmed by its presence as a process in Windows Task Manager.  The memory fluctuates as it goes about its business, but the script never runs, and the process never ends.

Does anyone know why changing the security setting causes MicroStation to not operate successfully?

MicroStation V8i v8.11.9.536
Windows 7 Pro SP1, 16Gb RAM, 64bit