(I couldn't find the log of what happened, so here's the MC crash report)

---- Minecraft Crash Report ----
// Don't be sad. I'll do better next time, I promise!

Time: 11/9/14 9:49 PM
Description: Updating screen events

java.lang.OutOfMemoryError: Java heap space
at java.awt.image.DataBufferInt.<init>(Unknown Source)
at java.awt.image.Raster.createPackedRaster(Unknown Source)
at java.awt.image.DirectColorModel.createCompatibleWritableRaster(Unknown Source)
at java.awt.image.BufferedImage.<init>(Unknown Source)
at cuj.a(SourceFile:407)
at cua.b(SourceFile:238)
at cua.a(SourceFile:77)
at cxh.j(SourceFile:553)
at cxh.a(SourceFile:139)
at cxk.a(SourceFile:23)
at cvt.c(SourceFile:104)
at cvt.a(SourceFile:92)
at bsu.e(SourceFile:641)
at bzx.a(SourceFile:161)
at bxf.a(SourceFile:342)
at bzx.a(SourceFile:169)
at bxf.k(SourceFile:405)
at bzx.k(SourceFile:74)
at bxf.p(SourceFile:382)
at bsu.r(SourceFile:1473)
at bsu.as(SourceFile:877)
at bsu.a(SourceFile:314)
at net.minecraft.client.main.Main.main(SourceFile:120)

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

– Head –
Stacktrace:
at java.awt.image.DataBufferInt.<init>(Unknown Source)
at java.awt.image.Raster.createPackedRaster(Unknown Source)
at java.awt.image.DirectColorModel.createCompatibleWritableRaster(Unknown Source)
at java.awt.image.BufferedImage.<init>(Unknown Source)
at cuj.a(SourceFile:407)
at cua.b(SourceFile:238)
at cua.a(SourceFile:77)
at cxh.j(SourceFile:553)
at cxh.a(SourceFile:139)
at cxk.a(SourceFile:23)
at cvt.c(SourceFile:104)
at cvt.a(SourceFile:92)
at bsu.e(SourceFile:641)
at bzx.a(SourceFile:161)
at bxf.a(SourceFile:342)
at bzx.a(SourceFile:169)
at bxf.k(SourceFile:405)
at bzx.k(SourceFile:74)
at bxf.p(SourceFile:382)

– Affected screen –
Details:
Screen name: bzx
Stacktrace:
at bsu.r(SourceFile:1473)
at bsu.as(SourceFile:877)
at bsu.a(SourceFile:314)
at net.minecraft.client.main.Main.main(SourceFile:120)

– System Details –
Details:
Minecraft Version: 1.8
Operating System: Windows 7 (x86) version 6.1
Java Version: 1.7.0_71, Oracle Corporation
Java VM Version: Java HotSpot(TM) Client VM (mixed mode), Oracle Corporation
Memory: 100577184 bytes (95 MB) / 523501568 bytes (499 MB) up to 523501568 bytes (499 MB)
JVM Flags: 6 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx512M -XX:+UseConcMarkSweepGC -XX:+CMSIncrementalMode -XX:-UseAdaptiveSizePolicy -Xmn128M
IntCache: cache: 0, tcache: 0, allocated: 13, tallocated: 95
Launched Version: 1.8
LWJGL: 2.9.1
OpenGL: Intel(R) HD Graphics 3000 GL version 3.1.0 - Build 9.17.10.3347, Intel
GL Caps: Using GL 1.3 multitexturing.
Using GL 1.3 texture combiners.
Using framebuffer objects because OpenGL 3.0 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