Flatworld chunks generating normal world terrain (difficult to reproduce)
Steps to Reproduce:
1. Create a superflat world.
Observed Result:
1 - Random chunks were generated with regular world terrain, not flat.
This seems to be a very rare bug. (These kind, I hate, since it can be a number of combinations). I had the render distance set to 32 chunks, but future superflat maps with 32 chunks loaded (same and different seed) didn't produce the bug. I also tried recreating the world with the same name (I've seen this happen before), and creating a custom generation world prior to the superflat world, but also didn't reproduce the glitch.
Environment
Windows 7 Ultimate, Java 7.0.1, 16 Gigs RAM (Minecraft uses 12 Gigs), ASUS p8z68, GTX 580
Created Issue:
Flatworld chunks generating normal world terrain (difficult to reproduce)
Steps to Reproduce:
1. Create a superflat world.
Observed Result:
1 - Random chunks were generated with regular world terrain, not flat.
This seems to be a very rare bug. (These kind, I hate, since it can be a number of combinations). I had the render distance set to 32 chunks, but future superflat maps with 32 chunks loaded (same and different seed) didn't produce the bug.
Environment
Windows 7 Ultimate, Java 7.0.1, 16 Gigs RAM (Minecraft uses 12 Gigs), ASUS p8z68, GTX 580
Steps to Reproduce:
1. Create a superflat world.
Observed Result:
1 - Random chunks were generated with regular world terrain, not flat.
This seems to be a very rare bug. (These kind, I hate, since it can be a number of combinations). I had the render distance set to 32 chunks, but future superflat maps with 32 chunks loaded (same and different seed) didn't produce the bug. I also tried recreating the world with the same name (I've seen this happen before), and creating a custom generation world prior to the superflat world, but also didn't reproduce the glitch.
duplicates

It could be the old and kind of tricky to get Chunk Resets which, from what I remember, use to reset the chunk if an invalid block was created/loaded. This is most likely fixed but it could be a possible explanation.