Re-launch MIT Learning Center course - error message

There is an intermittent problem with re-launching an eLearning course already in progress.  Very occasionally, a learner will try to launch an eLearning course and will receive the error below.  The solution is to close the browser window, then open a new browser window and try again.
          

NOTE: Learning should only view one MIT Learning Center course at a time.
Log off from one course before beginning a new course.