I was building a castle, and took a snapshot of it. About 15 seconds later, the game crashed.
The log says:
7/08/2015 5:46:06 PM
System.IndexOutOfRangeException: Index was outside the bounds of the array.
at Terraria.Lighting.LightTiles(Int32 firstX, Int32 lastX, Int32 firstY, Int32 lastY)...