Crashed to desktop with "argo/saj/InvalidSyntaxException"

--- Minecraft Crash Report ----
// Why did you do that?

Time: 6/30/13 11:54 PM
Description: Initializing game

java.lang.NoClassDefFoundError: argo/saj/InvalidSyntaxException
	at atn.O(SourceFile:344)
	at atn.d(SourceFile:598)
	at net.minecraft.client.main.Main.main(SourceFile:101)
Caused by: java.lang.ClassNotFoundException: argo.saj.InvalidSyntaxException
	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)
	... 3 more


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

-- Head --
Stacktrace:
	at atn.O(SourceFile:344)

-- Initialization --
Details:
Stacktrace:
	at atn.d(SourceFile:598)
	at net.minecraft.client.main.Main.main(SourceFile:101)

-- System Details --
Details:
	Minecraft Version: 1.6.1
	Operating System: Windows 7 (amd64) version 6.1
	Java Version: 1.6.0_29, Sun Microsystems Inc.
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Sun Microsystems Inc.
	Memory: 50425256 bytes (48 MB) / 128122880 bytes (122 MB) up to 954466304 bytes (910 MB)
	JVM Flags: 1 total; -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: 1.6.1
	LWJGL: 2.9.0
	OpenGL: GeForce GTX 560 Ti/PCIe/SSE2 GL version 4.3.0, NVIDIA Corporation
	Is Modded: Probably not. Jar signature remains and client brand is untouched.
	Type: Client (map_client.txt)
	Resource Pack: Default
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: ~~ERROR~~ NullPointerException: null