Hopper: java.lang.ClassFormatError: Truncated class file

This is an automatically generated report based from the following crash: http://hopper.minecraft.net/crashes/minecraft/MCX-64175/

Crash:

java.lang.ClassFormatError: Truncated class file
	at java.lang.ClassLoader.findBootstrapClass(Native Method)
	at java.lang.ClassLoader.findBootstrapClassOrNull(Unknown Source)
	at java.lang.ClassLoader.loadClass(Unknown Source)
	at java.lang.ClassLoader.loadClass(Unknown Source)
	at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
	at java.lang.ClassLoader.loadClass(Unknown Source)
	at blk.h(SourceFile:78)
	at blk.<init>(SourceFile:62)
	at ats.O(SourceFile:323)

The following is the first clean report made public about this crash:

---- Minecraft Crash Report ----
// I feel sad now :(

Time: 8/11/13 5:58 AM
Description: Initializing game

java.lang.ClassFormatError: Truncated class file
	at java.lang.ClassLoader.findBootstrapClass(Native Method)
	at java.lang.ClassLoader.findBootstrapClassOrNull(Unknown Source)
	at java.lang.ClassLoader.loadClass(Unknown Source)
	at java.lang.ClassLoader.loadClass(Unknown Source)
	at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
	at java.lang.ClassLoader.loadClass(Unknown Source)
	at blk.h(SourceFile:78)
	at blk.<init>(SourceFile:62)
	at ats.O(SourceFile:323)
	at ats.d(SourceFile:599)
	at net.minecraft.client.main.Main.main(SourceFile:101)


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

-- Head --
Stacktrace:
	at java.lang.ClassLoader.findBootstrapClass(Native Method)
	at java.lang.ClassLoader.findBootstrapClassOrNull(Unknown Source)
	at java.lang.ClassLoader.loadClass(Unknown Source)
	at java.lang.ClassLoader.loadClass(Unknown Source)
	at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
	at java.lang.ClassLoader.loadClass(Unknown Source)
	at blk.h(SourceFile:78)
	at blk.<init>(SourceFile:62)
	at ats.O(SourceFile:323)

-- Initialization --
Details:
Stacktrace:
	at ats.d(SourceFile:599)
	at net.minecraft.client.main.Main.main(SourceFile:101)

-- System Details --
Details:
	Minecraft Version: 1.6.2
	Operating System: Windows 7 (amd64) version 6.1
	Java Version: 1.7.0_21, Oracle Corporation
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
	Memory: 20145360 bytes (19 MB) / 44236800 bytes (42 MB) up to 954466304 bytes (910 MB)
	JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx1G
	AABB Pool Size: 0 (0 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
	Suspicious classes: No suspicious classes found.
	IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
	Launched Version: 1.6.2
	LWJGL: 2.9.0
	OpenGL: AMD M880G with ATI Mobility Radeon HD 4200   GL version 2.1.8787, ATI Technologies Inc.
	Is Modded: Probably not. Jar signature remains and client brand is untouched.
	Type: Client (map_client.txt)
	Resource Pack: Default
	Current Language: English (US)
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: ~~ERROR~~ NullPointerException: null

You can see this full report at http://hopper.minecraft.net/crashes/minecraft/MCX-64175/2066064/