All textures are white

What I expected to happen was
Blocks and items would all look the same as usual
What actually happened was
All blocks and items were white, with the exception of grass, ferns e.t.c. as they are coloured green by the game.
Steps to reproduce
Open a minecraft world

I assume this, like the white witch bug in 12w38b affects only some computers. I can attach a crash report if required.