We were running fine for a while on Myst 5 at the minimum system requirements until about 30 minutes into the game. Now we get massive, blotchy shadows over far-off objects until we get close, at which point they clear up.

Is this a graphics card problem? I have a nVidia GeForce 4. Problem is that I can't fix it by turning off shadows or by turning everything down in the video section - even with shadows off it still occurs.

Suggestions on overcoming this? It doesn't hinder gameplay, but it certainly takes away from the experience.

If you haven't already, take a look at (all 7 pages of) Myst V MacOS X crashes (full game).