Welp, I ended up deleting my old world completely and starting anew, but this message always stays open the entire time:
I can now play just fine, but that massive error message persists in the upper right corner the whole time and doesn't go away.
Even disabling the chat console in the option does nothing.
It seems I'll have to reinstall AVWW completely, hold my breath and cross my fingers that I wouldn't have another power outage while I'm playing it.