I am at least 1500 hours into a save.

Everything so far has been fine.

Today I loaded my world and began to explore a new area. My character would exit my spawn area via nether portal. I would exit the portal (an area that I have been working in) and began to travel in more or less a straight line diagonally. Within about five minutes of travelling the game would freeze for a second and then the game would close. I have tried relaunching and starting from where it crashed the game but the game crashes and closes again. I have tried restoring the game to an earlier point (app: 30 minutes) and then relaunching. The game loads but when I try to re-run the experiment (i.e - explore the same region) the game crashes and closes once again.