This has been going on for some time. For no good reason, my computer will start making "error" sounds. The sounds won't stop until I close down NextStart. When I do that, the Windows Error Reporting (WER) icon shows up on the Taskbar (it was not visible prior to closing NS). If I then close WER, I can open NS without any problems.

Open NextSTART Preferences, Sound & Animations tab. Is 'Beep when a task button is flashing on the taskbar' enabled?

YES! Thanks. Never would have found that. What purpose does that option serve?

Warn you by sound that an application requires your attention. Useful if you are not sitting right next to your PC but have your speakers turned on.