Do you use the world height anywhere? Bukkit has a method "getMaxHeight()" that will guarantee your plugin will work with either the current height, 1.2's height, or the height five years from now. Please use that instead of hardcoding 127! Also, if you use the sea level - don't just hardcode 64 or height/2, use world.getSeaLevel()! Do you use net.minecraft.server stuff, or build for CraftBukkit? Please don't! This is a *guaranteed* way that your plugin will break, and we can't help you when it does. Please review every use of you using that code and ask yourself if it's still needed - we've added a lot of cool new API lately that should remove the need for anyone to depend on CraftBukkit! Do you use any deprecated methods? We're planning to remove all deprecated methods (apart from Player.updateInventory()) in R5. Save yourself a lot of time and effort by making sure you're up to date with the latest code! Are you building with an old version of Bukkit? We may have changed some API around or deprecated some things since you last downloaded Bukkit. Go download the latest version now, compile and make sure it's all fine. If you're using maven, the latest <version> is "1.1-R4". Do you access any of Minecraft's save files directly? They're all changing in 1.2, so your plugin likely won't work correctly. Please make absolute sure that you still need to use these files, because we've added a lot of API recently which may be exactly what you need! Have a look at the latest specifics on what to change! It's just a few pages later in this topic!