Finally someone who posts the log
This further verifies that it's not FastCraft's fault. The components list FC prints after detecting a NullPointerException contains null entries, which will crash func_75068_a aka generateStructure. Check your log for entries like "Failed Piece with id" or "Skipping Piece with id".
By the looks of it this happens if a chunk is being populated near a structure which references components no longer available, e.g. if the mod providing the component was removed or said mod removed the component during an update.