See http://paste.ubuntu.com/10664959/

I've only had a quick look, but it seems like this mod may be responsible for loading a huge quantity of chunks, most likely unintentionally.

I'm not sure it's entirely my fault as serveral other mods are involved and I have no issue with Vanilla worldgen.
CustomMobSpawner does a EntityLiving.getCanSpawHere() inside the world gen and I'm not convinced it should.
That said, in my process, I need to check chunks adjacent to the passed coordinates, and that's probably why it loops too much.
Hopefully, adding if (world.getChunkProvider().chunkExists(cx, cz)) will fix that issue.