Hopper: java.lang.RuntimeException: Failed to check session lock, aborting

This is an automatically generated report based from the following crash: http://hopper.minecraft.net/crashes/minecraft/MCX-312557/

Crash:

java.lang.RuntimeException: Failed to check session lock, aborting
	at awo.h(SourceFile:48)
	at awo.<init>(SourceFile:34)
	at awk.<init>(SourceFile:16)
	at awl.a(SourceFile:71)
	at ayp.a(SourceFile:1573)
	at bau.a(SourceFile:202)
	at bbp.a(SourceFile:172)
	at bau.a(SourceFile:301)
	at bbp.d(SourceFile:236)
	at bbp.k(SourceFile:211)

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

---- Minecraft Crash Report ----
// Shall we play a game?

Time: 10/11/13 8:29 AM
Description: Updating screen events

java.lang.RuntimeException: Failed to check session lock, aborting
	at awo.h(SourceFile:48)
	at awo.<init>(SourceFile:34)
	at awk.<init>(SourceFile:16)
	at awl.a(SourceFile:71)
	at ayp.a(SourceFile:1573)
	at bau.a(SourceFile:202)
	at bbp.a(SourceFile:172)
	at bau.a(SourceFile:301)
	at bbp.d(SourceFile:236)
	at bbp.k(SourceFile:211)
	at ayp.o(SourceFile:1303)
	at ayp.ab(SourceFile:755)
	at ayp.e(SourceFile:706)
	at net.minecraft.client.main.Main.main(SourceFile:103)


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

-- Head --
Stacktrace:
	at awo.h(SourceFile:48)
	at awo.<init>(SourceFile:34)
	at awk.<init>(SourceFile:16)
	at awl.a(SourceFile:71)
	at ayp.a(SourceFile:1573)
	at bau.a(SourceFile:202)
	at bbp.a(SourceFile:172)
	at bau.a(SourceFile:301)
	at bbp.d(SourceFile:236)
	at bbp.k(SourceFile:211)

-- Affected screen --
Details:
	Screen name: bry
Stacktrace:
	at ayp.o(SourceFile:1303)
	at ayp.ab(SourceFile:755)
	at ayp.e(SourceFile:706)
	at net.minecraft.client.main.Main.main(SourceFile:103)

-- System Details --
Details:
	Minecraft Version: 13w41b
	Operating System: Mac OS X (x86_64) version 10.6.8
	Java Version: 1.6.0_51, Apple Inc.
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Apple Inc.
	Memory: 65031352 bytes (62 MB) / 97701888 bytes (93 MB) up to 1065025536 bytes (1015 MB)
	JVM Flags: 1 total; -Xmx1G
	AABB Pool Size: 0 (0 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
	IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
	Launched Version: 13w41b
	LWJGL: 2.9.0
	OpenGL: ATI Radeon HD 4670 OpenGL Engine GL version 2.1 ATI-1.6.36, ATI Technologies Inc.
	Is Modded: Probably not. Jar signature remains and client brand is untouched.
	Type: Client (map_client.txt)
	Resource Packs: []
	Current Language: English (US)
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: ~~ERROR~~ NullPointerException: null
	Anisotropic Filtering: Off (1)

You can see this full report at http://hopper.minecraft.net/crashes/minecraft/MCX-312557/16827629/