Mine craft doesn't run

Minecraft Crash Report ----
// Quite honestly, I wouldn't worry myself about that.

Time: 31/07/13 16:27
Description: Sending packet

java.lang.NullPointerException
at cm.b(SourceFile:116)
at cm.a(SourceFile:41)
at jz.b(SourceFile:421)
at hm.a(SourceFile:90)
at bkz.b(SourceFile:73)
at net.minecraft.server.MinecraftServer.t(SourceFile:488)
at net.minecraft.server.MinecraftServer.s(SourceFile:405)
at bkw.s(SourceFile:124)
at net.minecraft.server.MinecraftServer.run(SourceFile:339)
at hh.run(SourceFile:582)

A detailed walkthrough of the error, its code path and all known details is as follows:
---------------------------------------------------------------------------------------

– Head –
Stacktrace:
at cm.b(SourceFile:116)
at cm.a(SourceFile:41)

– Packet being sent –
Details:
Packet ID: 4
Packet class: fw
Stacktrace:
at jz.b(SourceFile:421)
at hm.a(SourceFile:90)
at bkz.b(SourceFile:73)
at net.minecraft.server.MinecraftServer.t(SourceFile:488)
at net.minecraft.server.MinecraftServer.s(SourceFile:405)
at bkw.s(SourceFile:124)
at net.minecraft.server.MinecraftServer.run(SourceFile:339)
at hh.run(SourceFile:582)

– System Details –
Details:
Minecraft Version: 1.6.2
Operating System: Windows 8 (x86) version 6.2
Java Version: 1.7.0_25, Oracle Corporation
Java VM Version: Java HotSpot(TM) Client VM (mixed mode, sharing), Oracle Corporation
Memory: 77377288 bytes (73 MB) / 168902656 bytes (161 MB) up to 518979584 bytes (494 MB)
JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx512M
AABB Pool Size: 950 (53200 bytes; 0 MB) allocated, 924 (51744 bytes; 0 MB) used
Suspicious classes: No suspicious classes found.
IntCache: cache: 0, tcache: 0, allocated: 1, tallocated: 63
Profiler Position: N/A (disabled)
Vec3 Pool Size: 1568 (87808 bytes; 0 MB) allocated, 1565 (87640 bytes; 0 MB) used
Player Count: 1 / 8; [ju['Player'/217, l='Demo_World', x=85.39, y=62.00, z=-50.69]]
Type: Integrated Server (map_client.txt)
Is Modded: Probably not. Jar signature remains and both client + server brands are untouched.Put the summary of the bug you're having here

What I expected to happen was...:
Describe what you thought should happen here

What actually happened was...:
Describe what happened here

Steps to Reproduce:
1. Put a step by step guide on how to trigger the bug here
2. ...
3. ...