1. I face east
2. I walk east for a short while, while still facing east
3. The game freezes, then crashes
4. I load it again, face north, south and west while walking east.
5. Don't crash.
6. Same as 4, but walking north south, and west.
7. Don't crash.
8. Face east, walk north, south, and west.
9. Don't crash.
10. Face east, try a few different paths eastbound.
11. Crashes every time.

I don't know what it is, but when I face east and walk east, it ALWAYS CRASHES 0.0 It's pretty specific, as when I cross a certain boundary with the above conditions, it will crash. Up until that point, however, I can keep walking east while facing east. The most ironic part is that it literally starts at my property line at its east-most part, extending north and south of that extended line.

One other thing I noticed is that at that point, all spawned entities, except for a single creeper, have des pawned past that line. Animals (sheep, pigs, cows, and chickens) can still walk around that area.

This world is fairly developed, as I've put in a few hours of work to building it, including a full tower, surface farm, underground farm, a couple mines, and the start of a bridge/railroad track. I don't know if, perhaps, since the mine is so developed underground, it causes the surface rendering to crash. Another option under the same terms could be that there is a development bug with infinite worlds.