Although, ironically, I was working on a cover of -ERROR when this happened. Two days ago I finally installed the V5.2 update since I'm an idiot and didn't notice it needed to be updated. The program ran fine for the rest of the day, but yesterday, an error message popped up when I tried to open the editor:
"UnhandledException: An unexpected error has occurred. VOCALOID5 Editor will now close." There was no error number.
I tried opening the editor via opening a .vpr file but that didn't work either.
I poked around some forums and I found a discussion on VocaVerse where someone else was having the problem. According to the people on the forum, Yamaha confirmed that this error came from .NET Framework. I don't know how to proceed, as all the ways for repairing .NET Framework I found are either outdated (Microsoft .NET Framework no longer shows under Control Panel) or are very confusing.
Secondly, I'm not sure if the person on VocaVerse was correct in saying Yamaha confirmed it came from .NET, since they didn't cite anything.
The discussion is here: vocaverse.network/threads/vocaloid-5-not-opening.951
I will also provide an image of the error.
Thanks for the support.