Bukkit

EDIT: I forgot to mention something important! The world seems to generate correctly, I can manually load it then tp to it and walk around.

Before anything else:
I'm using
    MCPC+ (git-MCPC-Plus-jenkins-MCPC-Plus-180) : v1_6_R3 (Minecraft 1.6.4) - http://ci.md-5.net/job/MCPC-Plus/180/
    BKCommonLib v1.56 - http://dev.bukkit.org/bukkit-plugins/bkcommonlib/files/48-v1-56/
    My World v1.66 - http://dev.bukkit.org/bukkit-plugins/my-worlds/files/44-v1-66/
with modpack "Direwolf20 (v1.0.5) Minecraft Version 1.6.4" without qCraft

So if you don't support modded servers, :(

What steps will reproduce the problem?
1. Creating a new world, I tested several times and the error seems to depend on the generated terrain.
2. example commands that generated the error on all 5 tests:
    /world create Twilight_twilightforest_biomesop VG
    >mw create Twilight_twilightforest_biomesop VG
3. example of commands that sometimes generate the error. (depends on seed?)
    >mw create SomeWorld << tested 3 times, third time generated the error
    >mw create Twilight << tested twice, first time generated the error
    >mw create Twilight VG << tested twice, first time generated the error

What is the expected output? What do you see instead?
    Expected to generate the world and load it.
    Instead the console gives a warning at 100% creation and the world is never loaded

What version of the product are you using?
    BKCommonLib v1.56 - http://dev.bukkit.org/bukkit-plugins/bkcommonlib/files/48-v1-56/
    My World v1.66 - http://dev.bukkit.org/bukkit-plugins/my-worlds/files/44-v1-66/

Do you have an error log of what happened?
    Yes, a small compilation of when the error happened and didn't happened. Sometimes both with the same command. Hope you don't mind pastebin!
    http://pastebin.com/3T8EnQXc

Please provide any additional information below.
    some incompatibility with custom blocks maybe?
    My best guess would be an error while searching for a safe location of the spawn point. But that's only a guess :)

edit to add important info to line 1