Thanks, I did eventually find an answer - difficult to find search terms for this problem!
I'm just wondering what that solution was.
I recently upgraded to 10.6.8 (I know I'm years behind) and have also had the red screen and other graphics issues. The game played fine for years under 10.4.11. Every graphic is at low and that aliasing is at 0.
It's been suggested to me that it's my graphic driver (Intel GMA 950) that's the issue, but if there's a different fix, I would prefer it.
Even if there's no fix, I would just love to know why a better OS broke my favourite game.