On occasion the LabTutor Kernel may not close properly when closing down LabAuthor / LabTutor. This is indicated by the Kernel icon remaining in the System tray after you have closed LabAuthor / LabTutor:
Prior to opening LabAuthor / LabTutor, you should close the Kernel by right-clicking on it in the System Tray, and selecting Exit LabTutor Kernel.
If the Kernel is already open prior to opening LabAuthor / LabTutor, then the Kernel components may not function correctly (whilst the Kernel is 'open' it wouldn't be communicating with this particular instance of LabAuthor / LabTutor).