I think it was just heat, whenever I get my A1200 out I generally put it on my bed, which isn't great for ventilation lol and I'm not accustomed with having a steaming accelerator in there, next time I'm just gonna make sure it's on a solid flat surface and I'm going to modify the trapdoor for ventilation too!
Glad I found this game though, shows what the A1200 can do with a bit more CPU power, even if the cars handle horribly lol
Robert