[Game crashes when I try to open my world]

When I try to open my world my game crashes. I uninstalled the game and reinstalled, got a new version of java, and I saved the save of my world and put it in the folder and it won't open but I can create a new world and play on it.

This is the crash report I think.

java.lang.NullPointerException: 

    at net.minecraft.world.gen.structure.StructureStart.func_75068_a(StructureStart.java:47)
    at net.minecraft.world.gen.structure.MapGenStructure.func_75051_a(MapGenStructure.java:81)
    at net.minecraft.world.gen.ChunkProviderGenerate.func_73153_a(ChunkProviderGenerate.java:533)
    at net.minecraft.world.gen.ChunkProviderServer.func_73153_a(ChunkProviderServer.java:258)
    at net.minecraft.world.chunk.Chunk.func_76624_a(Chunk.java:1253)
    at net.minecraft.world.gen.ChunkProviderServer.func_73158_c(ChunkProviderServer.java:153)
    at net.minecraft.server.management.PlayerInstance.<init>(PlayerInstance.java:43)
    at net.minecraft.server.management.PlayerManager.func_72690_a(SourceFile:208)
    at net.minecraft.server.management.PlayerManager.func_72683_a(SourceFile:240)
    at net.minecraft.server.management.ServerConfigurationManager.func_72375_a(ServerConfigurationManager.java:220)
    at net.minecraft.server.management.ServerConfigurationManager.func_72377_c(ServerConfigurationManager.java:268)
    at net.minecraft.server.management.ServerConfigurationManager.func_72355_a(ServerConfigurationManager.java:136)
    at net.minecraft.server.integrated.IntegratedServerListenThread.func_71747_b(IntegratedServerListenThread.java:97)
    at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:691)
    at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:587)
    at net.minecraft.server.integrated.IntegratedServer.func_71217_p(IntegratedServer.java:129)
    at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:484)
    at net.minecraft.server.ThreadMinecraftServer.run(SourceFile:583)