my minecraft randomly crashes and runs out of memory

---- Minecraft Crash Report ----
// I feel sad now :(

Time: 5/17/13 9:11 AM
Description: Updating screen events

java.lang.OutOfMemoryError: unable to create new native thread
	at java.lang.Thread.start0(Native Method)
	at java.lang.Thread.start(Unknown Source)
	at java.util.Timer.<init>(Unknown Source)
	at ma.<init>(SourceFile:22)
	at net.minecraft.server.MinecraftServer.<init>(SourceFile:43)
	at bjg.<init>(SourceFile:35)
	at net.minecraft.client.Minecraft.a(SourceFile:1378)
	at axu.e(SourceFile:166)
	at axu.a(SourceFile:131)
	at axr.a(SourceFile:72)
	at axr.d(SourceFile:127)
	at axr.m(SourceFile:111)
	at net.minecraft.client.Minecraft.l(SourceFile:1078)
	at net.minecraft.client.Minecraft.K(SourceFile:574)
	at net.minecraft.client.Minecraft.run(SourceFile:526)
	at java.lang.Thread.run(Unknown Source)


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

-- Head --
Stacktrace:
	at java.lang.Thread.start0(Native Method)
	at java.lang.Thread.start(Unknown Source)
	at java.util.Timer.<init>(Unknown Source)
	at ma.<init>(SourceFile:22)
	at net.minecraft.server.MinecraftServer.<init>(SourceFile:43)
	at bjg.<init>(SourceFile:35)
	at net.minecraft.client.Minecraft.a(SourceFile:1378)
	at axu.e(SourceFile:166)
	at axu.a(SourceFile:131)
	at axr.a(SourceFile:72)
	at axr.d(SourceFile:127)
	at axr.m(SourceFile:111)

-- Affected screen --
Details:
	Screen name: bkf
Stacktrace:
	at net.minecraft.client.Minecraft.l(SourceFile:1078)
	at net.minecraft.client.Minecraft.K(SourceFile:574)
	at net.minecraft.client.Minecraft.run(SourceFile:526)
	at java.lang.Thread.run(Unknown Source)

-- System Details --
Details:
	Minecraft Version: 1.5.2
	Operating System: Windows 7 (x86) version 6.1
	Java Version: 1.7.0_21, Oracle Corporation
	Java VM Version: Java HotSpot(TM) Client VM (mixed mode), Oracle Corporation
	Memory: 420385824 bytes (400 MB) / 519110656 bytes (495 MB) up to 1037959168 bytes (989 MB)
	JVM Flags: 2 total; -Xms512m -Xmx1024m
	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: 1, tallocated: 63
	LWJGL: 2.4.2
	OpenGL: Intel(R) HD Graphics GL version 2.1.0 - Build 8.15.10.2372, Intel
	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

I was trying to dig/mine.
The game says --Minecraft has crashed--,says minecraft has run out of memory, or freezes and disappears

TO RECREATE
step one: join a world
step two: preform any task
step three: watch your game lag and crash, run out of memory, or disappear