பயர்பாக்ஸ் ஆதரவு மன்றம்

Windows 10. Weird glitch.

If I use Wondershare UniConverter's downloader function to download a video, as soon as the download starts, all Firefox open windows close. This is a recent thing, the last couple of weeks or so. I have reinstalled Firefox and UniConverter. The first time I tried it after reinstalling UniConverter, all was well. But the same issue has shown up again. I have tried rebooting my PC to no effect.

Any bright ideas welcome!