Minecraft – Strange polygons appear in fullscreen

Another interesting Minecraft "feature" here. When I play from inside the browser and hit F11 for fullscreen, I get wildly moving polygons flashing across the entire screen:

It doesn't affect character movement or button triggers, but it makes the game world hard to navigate. There are about 30 of these polygonal messes per second, and it makes me dizzy to try and ignore and play through it. Strangely, the in-game GUIs are fairly easy to see, though are not entirely unscathed by the polygons.

Has anyone else experienced similar problems with in-browser fullscreen? Is there a way to fix it, perhaps by changing my display settings or browser Java settings somehow?