When I launch my singleplayer Direwolf 1.6.4 it shuts down FTB

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The same thing is happening to me. However, I disabled Thaumcraft and it let me load a new world.
 
I believe when this happens your world has become corrupted. Restore from a backup if you have it and if not then you will need to create a new world.
Sadly i didn't have a backup, so it seems i will be creating a new world