if you are just starting the game, they might be dying because of starvation or just possibly sickness. there is no glitch that makes villagers die, at least one that LadyCFII or Arthur knows about...
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things happen when you least expect them, like GC's parties, and they happen right when you've finally gotten everybody working
And help the VV's by Copying this into your signiture,
Pm me when your done copying!

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8\)
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Villagers population: 6.