Unexpected error on server in a certain area.

1. What OS are you using (Brand and version - Ex. Windows XP SP3)?
Windows 7

2. What architecture is the OS you are running (x64 or x86)?
x86

3. What version and architecture is your java install? (Type: java -version in command prompt.)
java version "1.6.0_24"

Code:

 Failed to handle packet: java.lang.NullPointerException
java.lang.NullPointerException
	at net.minecraft.server.ItemStack.d(ItemStack.java:95)
	at net.minecraft.server.ItemStack.f(ItemStack.java:103)
	at net.minecraft.server.InventoryPlayer.canHold(InventoryPlayer.java:124)
	at net.minecraft.server.EntityItem.b(EntityItem.java:205)
	at net.minecraft.server.EntityHuman.i(EntityHuman.java:212)
	at net.minecraft.server.EntityHuman.u(EntityHuman.java:204)
	at net.minecraft.server.EntityPlayer.u(EntityPlayer.java:212)
	at net.minecraft.server.EntityLiving.p_(EntityLiving.java:231)
	at net.minecraft.server.EntityHuman.p_(EntityHuman.java:90)
	at net.minecraft.server.EntityPlayer.a(EntityPlayer.java:169)
	at net.minecraft.server.NetServerHandler.a(NetServerHandler.java:273)
	at net.minecraft.server.Packet10Flying.a(SourceFile:126)
	at net.minecraft.server.NetworkManager.a(NetworkManager.java:196)
	at net.minecraft.server.NetServerHandler.a(NetServerHandler.java:75)
	at net.minecraft.server.NetworkListenThread.a(SourceFile:100)
	at net.minecraft.server.MinecraftServer.h(MinecraftServer.java:372)
	at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:287)
	at net.minecraft.server.ThreadServerApplication.run(SourceFile:394)

EDIT: Fixed it somehow telling other people to go into the area and resetting the server a lot of times.