Terrain not loading in all worlds

Terrain in all worlds (those created in 14w30 and those created earlier) no longer loads in. When I load a world I just fall into the abyss with no visible blocks.

I did play in 14w30c for a few hours without any problems before this started happening. I've not been able to get terrain to load in this snapshot since.

EDIT: Worlds opened in 14w30c now get stuck on the "downloading terrain" screen. Worlds loaded in 1.7.10 (even new worlds generated in 1.7.10) crash upon opening. Crash report here: http://pastebin.com/vnYE3hJ7