— Minecraft Crash Report ----
// You should try our sister game, Minceraft!

Time: 7/8/15 12:05 PM
Description: Updating screen events

java.lang.RuntimeException: Failed to check session lock, aborting
at atm.h(SourceFile:49)
at atm.<init>(SourceFile:35)
at atj.<init>(SourceFile:19)
at atk.a(SourceFile:78)
at ave.a(SourceFile:1900)
at axb.a(SourceFile:210)
at axu.a(SourceFile:350)
at axb.a(SourceFile:350)
at axu.k(SourceFile:413)
at axu.p(SourceFile:390)
at ave.s(SourceFile:1497)
at ave.av(SourceFile:888)
at ave.a(SourceFile:325)
at net.minecraft.client.main.Main.main(SourceFile:124)

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

– Head –
Stacktrace:
at atm.h(SourceFile:49)
at atm.<init>(SourceFile:35)
at atj.<init>(SourceFile:19)
at atk.a(SourceFile:78)
at ave.a(SourceFile:1900)
at axb.a(SourceFile:210)
at axu.a(SourceFile:350)
at axb.a(SourceFile:350)
at axu.k(SourceFile:413)
at axu.p(SourceFile:390)

– Affected screen –
Details:
Screen name: aya
Stacktrace:
at ave.s(SourceFile:1497)
at ave.av(SourceFile:888)
at ave.a(SourceFile:325)
at net.minecraft.client.main.Main.main(SourceFile:124)

– System Details –
Details:
Minecraft Version: 1.8.7
Operating System: Mac OS X (x86_64) version 10.6.8
CPU: 2x Intel(R) Core(TM)2 Duo CPU P8600 @ 2.40GHz
Java Version: 1.6.0_65, Apple Inc.
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Apple Inc.
Memory: 172905744 bytes (164 MB) / 237899776 bytes (226 MB) up to 1060372480 bytes (1011 MB)
JVM Flags: 5 total; -Xmx1G -XX:+UseConcMarkSweepGC -XX:+CMSIncrementalMode -XX:-UseAdaptiveSizePolicy -Xmn128M
IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
Launched Version: 1.8.7
LWJGL: 2.9.2
OpenGL: NVIDIA GeForce 320M OpenGL Engine GL version 2.1 NVIDIA-1.6.36, NVIDIA Corporation
GL Caps: Using GL 1.3 multitexturing.
Using GL 1.3 texture combiners.
Using framebuffer objects because ARB_framebuffer_object is supported and separate blending is supported.
Shaders are available because OpenGL 2.1 is supported.
VBOs are available because OpenGL 1.5 is supported.

Using VBOs: No
Is Modded: Probably not. Jar signature remains and client brand is untouched.
Type: Client (map_client.txt)
Resource Packs: []
Current Language: English (UK)
Profiler Position: N/A (disabled)