There is no slot043.gsi in my save folder, actually. Same for the other saves. It never happened again anyway, so I have a feeling something in that save just got messed up with spell animations. But this time I seem to have run into an actually gamebreaking issue - I cannot progress to Nulb. On the way there, I invariably encounter the caravan slaughtered by gnolls, but other than some guilt-tripping for not adhering to D&D's creepy racial determinism earlier there does not seem to be anything to do there. When I try to move on to Nulb from that area though, the game freezes on the world map. Buttons and other destinations still highlight, but clicking them does nothing at all.