cant play multiplayer or singleplayer

Every time i join a server it just crashes minecraft i cant even play and when i start a world or create one it just freezes minecraft until i quit out of it

heres what it says when i join a server

---- Minecraft Crash Report ----
// Hi. I'm Minecraft, and I'm a crashaholic.

Time: 10/30/12 3:32 PM
Description: Unexpected error

java.lang.NoClassDefFoundError: abd
	at java.lang.ClassLoader.defineClass1(Native Method)
	at java.lang.ClassLoader.defineClassCond(ClassLoader.java:631)
	at java.lang.ClassLoader.defineClass(ClassLoader.java:615)
	at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:141)
	at java.net.URLClassLoader.defineClass(URLClassLoader.java:283)
	at java.net.URLClassLoader.access$000(URLClassLoader.java:58)
	at java.net.URLClassLoader$1.run(URLClassLoader.java:197)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
	at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:295)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
	at xz.<init>(SourceFile:122)
	at yn.<init>(SourceFile:6)
	at xz.<clinit>(SourceFile:18)
	at ye.<init>(SourceFile:20)
	at ye.<init>(SourceFile:30)
	at ye.<init>(SourceFile:38)
	at zr.b(SourceFile:44)
	at zr.a(SourceFile:27)
	at xe.<init>(SourceFile:126)
	at awz.<init>(SourceFile:39)
	at awr.a(SourceFile:148)
	at do.a(SourceFile:71)
	at bx.b(SourceFile:341)
	at awr.d(SourceFile:98)
	at awu.c(SourceFile:69)
	at net.minecraft.client.Minecraft.l(SourceFile:1080)
	at net.minecraft.client.Minecraft.J(SourceFile:582)
	at net.minecraft.client.Minecraft.run(SourceFile:534)
	at java.lang.Thread.run(Thread.java:680)
Caused by: java.lang.ClassNotFoundException: abd
	at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
	at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
	... 32 more

Relevant Details:
- Minecraft Version: 1.4.2
- Operating System: Mac OS X (x86_64) version 10.6.8
- Java Version: 1.6.0_37, Apple Inc.
- Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Apple Inc.
- Memory: 516765584 bytes (492 MB) / 554369024 bytes (528 MB) up to 1069416448 bytes (1019 MB)
- JVM Flags: 3 total; -Xbootclasspath/a:/System/Library/PrivateFrameworks/JavaApplicationLauncher.framework/Resources/LauncherSupport.jar -Xms512M -Xmx1024M
- AABB Pool Size: 0 (0 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
- LWJGL: 2.4.2
- OpenGL: ATI Radeon HD 4670 OpenGL Engine GL version 2.1 ATI-1.6.36, ATI Technologies Inc.
- Is Modded: Probably not
- Type: Client
- Texture Pack: Default