It says i left the game when i join it

When I log into my own local server, it tells the other players that I joined the game, joined, left,, left... and left. But I am on the server, people see me, but some of the commands won't work with my name. See pictures below.

I have deleted all players' .dat file, reset the scoreboard to fix this, but it still happens frequently

(My username is torokt21)

---- Minecraft Crash Report ----
// I let you down. Sorry :(

Time: 2014.01.29. 21:11
Description: Manually triggered debug crash

java.lang.Throwable
	at bby.p(SourceFile:1437)
	at bby.aj(SourceFile:774)
	at bby.f(SourceFile:728)
	at net.minecraft.client.main.Main.main(SourceFile:154)


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

-- Head --
Stacktrace:
	at bmw.a(SourceFile:298)

-- Affected level --
Details:
	Level name: MpServer
	All players: 1 total; [boy['torokt21'/4065, l='MpServer', x=1068,33, y=67,82, z=873,47]]
	Chunk stats: MultiplayerChunkCache: 841, 841
	Level seed: 0
	Level generator: ID 00 - default, ver 1. Features enabled: false
	Level generator options: 
	Level spawn location: 255,00,72,00,275,00 - World: (255,72,275), Chunk: (at 15,4,3 in 15,17; contains blocks 240,0,272 to 255,255,287), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
	Level time: 14232267 game time, 1 day time
	Level dimension: 0
	Level storage version: 0x00000 - Unknown?
	Level weather: Rain time: 0 (now: false), thunder time: 0 (now: false)
	Level game mode: Game mode: creative (ID 1). Hardcore: false. Cheats: false
	Forced entities: 29 total; [sp['entity.ItemFrame.name'/4020, l='MpServer', x=956,06, y=51,50, z=862,50], sp['entity.ItemFrame.name'/4021, l='MpServer', x=954,06, y=51,50, z=861,50], sp['entity.ItemFrame.name'/4022, l='MpServer', x=952,94, y=51,50, z=861,50], sp['entity.ItemFrame.name'/4017, l='MpServer', x=958,06, y=51,50, z=862,50], sp['entity.ItemFrame.name'/4018, l='MpServer', x=956,94, y=51,50, z=862,50], sp['entity.ItemFrame.name'/4019, l='MpServer', x=954,94, y=51,50, z=862,50], sp['entity.ItemFrame.name'/4028, l='MpServer', x=954,94, y=51,50, z=868,50], sp['entity.ItemFrame.name'/4029, l='MpServer', x=956,94, y=51,50, z=868,50], sp['entity.ItemFrame.name'/4030, l='MpServer', x=956,06, y=51,50, z=868,50], sp['entity.ItemFrame.name'/4031, l='MpServer', x=958,06, y=51,50, z=868,50], sp['entity.ItemFrame.name'/4026, l='MpServer', x=952,94, y=51,50, z=868,50], sp['entity.ItemFrame.name'/4027, l='MpServer', x=954,06, y=51,50, z=868,50], sp['entity.ItemFrame.name'/4034, l='MpServer', x=1085,50, y=79,50, z=891,94], sp['entity.ItemFrame.name'/4033, l='MpServer', x=1083,50, y=79,50, z=891,94], sp['entity.ItemFrame.name'/4043, l='MpServer', x=960,50, y=51,50, z=866,06], sp['entity.ItemFrame.name'/4047, l='MpServer', x=1083,50, y=106,50, z=863,94], sp['entity.ItemFrame.name'/4046, l='MpServer', x=1084,50, y=106,50, z=863,94], sp['entity.ItemFrame.name'/4044, l='MpServer', x=960,50, y=51,50, z=864,94], zm['arrow'/4050, l='MpServer', x=1091,28, y=52,16, z=831,03], zm['arrow'/4051, l='MpServer', x=1089,28, y=53,00, z=840,69], zm['arrow'/4048, l='MpServer', x=1073,38, y=52,25, z=872,97], boy['torokt21'/4065, l='MpServer', x=1068,33, y=67,82, z=873,47], zm['arrow'/4049, l='MpServer', x=1091,41, y=52,38, z=831,03], zm['arrow'/4054, l='MpServer', x=1091,69, y=52,44, z=832,03], zm['arrow'/4052, l='MpServer', x=1090,03, y=51,81, z=841,34], boz['torokt21'/4064, l='MpServer', x=1078,44, y=66,19, z=890,91], zm['arrow'/4053, l='MpServer', x=1091,25, y=52,19, z=832,03], sq['entity.LeashKnot.name'/4062, l='MpServer', x=966,50, y=56,50, z=863,50], sq['entity.LeashKnot.name'/4063, l='MpServer', x=966,50, y=56,50, z=867,50]]
	Retry entities: 0 total; []
	Server brand: vanilla
	Server type: Non-integrated multiplayer server
Stacktrace:
	at bmw.a(SourceFile:298)
	at bby.b(SourceFile:2029)
	at bby.f(SourceFile:737)
	at net.minecraft.client.main.Main.main(SourceFile:154)

-- System Details --
Details:
	Minecraft Version: 14w04b
	Operating System: Windows 8 (amd64) version 6.2
	Java Version: 1.7.0_51, Oracle Corporation
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
	Memory: 512128040 bytes (488 MB) / 707264512 bytes (674 MB) up to 954728448 bytes (910 MB)
	JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx1G
	IntCache: cache: 0, tcache: 0, allocated: 13, tallocated: 95
	Launched Version: 14w04b
	LWJGL: 2.9.1
	OpenGL: AMD Radeon HD 5700 Series GL version 4.3.12618 Compatibility Profile Context 13.251.0.0, ATI Technologies Inc.
	GL Caps: Using GL 1.3 multitexturing.
Using framebuffer objects because OpenGL 3.0 is supported and separate blending is supported.
Anisotropic filtering is supported and maximum anisotropy is 16.
Shaders are available because OpenGL 2.1 is supported.

	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)
	Anisotropic Filtering: Off (1)