EDIT: Just fixed that issue. It was a problem with those ChunkProviders. Derp. Sorry 'bout this. If anyone is having those issues, add this to your ChunkProvider:
/**
* Returns a list of creatures of the specified type that can spawn at the given location.
*/
public List getPossibleCreatures(EnumCreatureType par1EnumCreatureType, int par2, int par3, int par4)
{
BiomeGenBase var5 = this.worldObj.getBiomeGenForCoords(par2, par4);
return var5 == null ? null : var5.getSpawnableList(par1EnumCreatureType);
}