Hopper: java.lang.SecurityException: SHA1 digest error for bfi.class

This is an automatically generated report based from the following crash: http://hopper.minecraft.net/crashes/minecraft/MCX-3521/

Crash:

java.lang.SecurityException: SHA1 digest error for bfi.class
	at sun.security.util.ManifestEntryVerifier.verify(Unknown Source)
	at java.util.jar.JarVerifier.processEntry(Unknown Source)
	at java.util.jar.JarVerifier.update(Unknown Source)
	at java.util.jar.JarVerifier$VerifierStream.read(Unknown Source)
	at sun.misc.Resource.getBytes(Unknown Source)
	at java.net.URLClassLoader.defineClass(Unknown Source)
	at java.net.URLClassLoader.access$100(Unknown Source)
	at java.net.URLClassLoader$1.run(Unknown Source)
	at java.net.URLClassLoader$1.run(Unknown Source)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.net.URLClassLoader.findClass(Unknown Source)
	at java.lang.ClassLoader.loadClass(Unknown Source)
	at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
	at java.lang.ClassLoader.loadClass(Unknown Source)
	at ats.O(SourceFile:376)

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

---- Minecraft Crash Report ----
// I bet Cylons wouldn't have this problem.

Time: 02/08/13 10:53
Description: Initializing game

java.lang.SecurityException: SHA1 digest error for bfi.class
	at sun.security.util.ManifestEntryVerifier.verify(Unknown Source)
	at java.util.jar.JarVerifier.processEntry(Unknown Source)
	at java.util.jar.JarVerifier.update(Unknown Source)
	at java.util.jar.JarVerifier$VerifierStream.read(Unknown Source)
	at sun.misc.Resource.getBytes(Unknown Source)
	at java.net.URLClassLoader.defineClass(Unknown Source)
	at java.net.URLClassLoader.access$100(Unknown Source)
	at java.net.URLClassLoader$1.run(Unknown Source)
	at java.net.URLClassLoader$1.run(Unknown Source)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.net.URLClassLoader.findClass(Unknown Source)
	at java.lang.ClassLoader.loadClass(Unknown Source)
	at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
	at java.lang.ClassLoader.loadClass(Unknown Source)
	at ats.O(SourceFile:376)
	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 sun.security.util.ManifestEntryVerifier.verify(Unknown Source)
	at java.util.jar.JarVerifier.processEntry(Unknown Source)
	at java.util.jar.JarVerifier.update(Unknown Source)
	at java.util.jar.JarVerifier$VerifierStream.read(Unknown Source)
	at sun.misc.Resource.getBytes(Unknown Source)
	at java.net.URLClassLoader.defineClass(Unknown Source)
	at java.net.URLClassLoader.access$100(Unknown Source)
	at java.net.URLClassLoader$1.run(Unknown Source)
	at java.net.URLClassLoader$1.run(Unknown Source)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.net.URLClassLoader.findClass(Unknown Source)
	at java.lang.ClassLoader.loadClass(Unknown Source)
	at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
	at java.lang.ClassLoader.loadClass(Unknown Source)
	at ats.O(SourceFile:376)

-- 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 (x86) version 6.1
	Java Version: 1.7.0_07, Oracle Corporation
	Java VM Version: Java HotSpot(TM) Client VM (mixed mode, sharing), Oracle Corporation
	Memory: 33958320 bytes (32 MB) / 67465216 bytes (64 MB) up to 518979584 bytes (494 MB)
	JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx512M
	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 Radeon(TM) HD 6480G GL version 4.1.11156 Compatibility Profile Context, 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 (UK)
	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-3521/32153/