When entering nether, game hangs on "building terrain screen"

When entering the nether, the game gets stuck on the loading screen that says "building terrain." All sounds indicate that I have entered the nether successfully, but the screen shows otherwise. When I force quit the game (no way to save&quit when stuck on that screen) and relaunch, the nether is fine. I have been entering and exiting the nether frequently for resources and find that one time I enter it loads in quickly and properly, and 10 minutes later it hangs.