Wind Waker graphical problem

[Philljc]

I keep getting this problem on the Dragon Roost island dungeon. Black squares fill the screen and travel upwards really fast, as if replacing the little fire embers.

Here is a screenshot (click for a bigger one):



i7, GTX295, 6GB RAM, Dolphin 4710

I have tried OpenGL and Direct 3D. Nothing I change seems to matter. Up until this point the game ran flawlessly. Any ideas?