My computer's cooling fan was on full blast, so I turned my Smooth Lighting down from Minimum to OFF, Render Distance from 16 to 14, and also turned off VSync and Use VBOs. Later, I decided to turn them back up, and two large cubic areas of my world had turned into masses of tangled black panels with a blue microchip-esque texture on them. I panicked and reloaded my world until they were gone, so I unfortunately failed to get a screenshot.

EDIT: Was able to replicate!

LAST EDIT: On closer inspection, these "microchips" are every texture strung together into one plane.