[MC-4947] Constant crashing when starting Minecraft

Recently, whenever I open Minecraft I have been greeted by a crash report and I can't even play the game! I am just playing vanilla Minecraft without mods and I have tried all that I can think of like re-installing the game and nothing works! Any help or possible solutions would be greatly appreciated!

Here is a crash report, they're all the same:
// Oops.

Time: 12/18/12 5:18 PM
Description: Failed to start game

java.lang.NullPointerException
	at java.io.Reader.<init>(Reader.java:61)
	at java.io.InputStreamReader.<init>(InputStreamReader.java:80)
	at bn.a(SourceFile:56)
	at bn.a(SourceFile:91)
	at net.minecraft.client.Minecraft.a(SourceFile:249)
	at net.minecraft.client.Minecraft.run(SourceFile:515)
	at java.lang.Thread.run(Thread.java:680)


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

-- System Details --
Details:
	Minecraft Version: 1.4.5
	Operating System: Mac OS X (x86_64) version 10.8.2
	Java Version: 1.6.0_37, Apple Inc.
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Apple Inc.
	Memory: 1020401648 bytes (973 MB) / 1071579136 bytes (1021 MB) up to 2143158272 bytes (2043 MB)
	JVM Flags: 3 total; -Xbootclasspath/a:/System/Library/PrivateFrameworks/JavaApplicationLauncher.framework/Resources/LauncherSupport.jar -Xms1024M -Xmx2048M
	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
	LWJGL: 2.4.2
	OpenGL: NVIDIA GeForce 9400M OpenGL Engine GL version 2.1 NVIDIA-8.0.61, NVIDIA Corporation
	Is Modded: Probably not. Jar signature remains and client brand is untouched.
	Type: Client (map_client.txt)
	Texture Pack: Default
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: ~~ERROR~~ NullPointerException: null