Is it on a computer with good internet access?

In the case of the event software shutting down, I'd installed the latest version the previous evening, at which point I assume a copy had been uploaded to MS for testing. It was the next morning after getting an internet connection setup having dealt with the initial rush, all the software shut down, which I'm guessing is the point the virus checker got details about the software being infected back from MS.

It could be MS have discovered some new virus that matches something in UCNC, so it's only just being flagged. If it is a false positive it should sort itself out in a couple days and stop being flagged.