The error message indicates that the Lab 100 software is still in use long after it has been closed.
There is a MSU Replication process that takes a little while to initiate after shutting down the Lab 100 software. After a few minutes, you’ll likely see a message on your screen similar to the one shown below (click image to enlarge).
Wait about 5 minutes from the time you close Lab 100, and after the replication process has completed, before shutting down the computer. If you don’t, you’ll get a message when starting Lab 100 the next time that indicates it wasn’t shut down properly previously. This is because the replication process hadn’t completed.