Whenever I go onto my server (and only on my server, not anything else), hosted from my friend's computer, I often crash. This crash is triggered by either by using a teleportation plugin, or by changing worlds. Gamemode does not matter, though I've noticed it sometimes takes a VERY long time to switch gamemodes upon arriving on a new world. Right now, after doing some WorldEditing, I put a couple of lava blocks and now, I continually crash. I tried deleting my player.dat file, but I still can't get away from the crash. I can't do anything. The server itself is fine, and I am not running any mods. Other people who go on my server have also experienced this problem. I currently have about 12 worlds on my server, though most of them are very small (less than 500 blocks by 500 blocks loaded).

Here was the latest crash screen:

Minecraft has crashed!
----------------------

Minecraft has stopped running because it encountered a problem; Exception in world tick

A full error report has been saved to C:\Users\Op\AppData\Roaming\.minecraft\crash-reports\crash-2013-04-27_19.12.34-client.txt - Please include a copy of that file (Not this screen!) if you report this crash to anyone; without it, they will not be able to help fix the crash

— BEGIN ERROR REPORT c547e87d --------
Full report at:
C:\Users\Op\AppData\Roaming\.minecraft\crash-reports\crash-2013-04-27_19.12.34-client.txt
Please show that file to Mojang, NOT just this screen!

Generated 27/04/13 7:12 PM

– Head –
Stacktrace:
at arj.b(SourceFile:210)
at bdl.a(SourceFile:1145)
at fd.a(SourceFile:99)
at ci.b(SourceFile:350)
at bdl.d(SourceFile:95)

– Affected level –
Details:
Level name: MpServer
All players: 1 total; [bdw['McF4rtson'/2179, l='MpServer', x=326.99, y=88.62, z=-20.96]]
Chunk stats: MultiplayerChunkCache: 160
Level seed: 0
Level generator: ID 00 - default, ver 1. Features enabled: false
Level generator options:
Level spawn location: World: (0,64,0), Chunk: (at 0,4,0 in 0,0; contains blocks 0,0,0 to 15,255,15), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
Level time: 1711795 game time, 1711795 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: survival (ID 0). Hardcore: false. Cheats: false
Forced entities: 30 total; [bdw['McF4rtson'/2179, l='MpServer', x=326.99, y=88.62, z=-20.96], qn['Pig'/2200, l='MpServer', x=351.31, y=67.00, z=-88.50], rh['item.item.porkchopRaw'/2201, l='MpServer', x=377.78, y=67.13, z=-64.06], qn['Pig'/2202, l='MpServer', x=300.22, y=64.00, z=-95.84], qn['Pig'/2203, l='MpServer', x=352.06, y=65.00, z=-84.03], rj['entity.MinecartChest.name'/2205, l='MpServer', x=285.50, y=11.69, z=37.50], qg['Bat'/2206, l='MpServer', x=258.53, y=23.10, z=-75.91], qg['Bat'/2207, l='MpServer', x=265.56, y=40.10, z=-71.00], qn['Pig'/2192, l='MpServer', x=352.47, y=67.00, z=-70.31], qn['Pig'/2193, l='MpServer', x=376.19, y=67.00, z=-58.50], qg['Bat'/2194, l='MpServer', x=268.75, y=17.10, z=-26.25], qn['Pig'/2195, l='MpServer', x=261.31, y=63.00, z=-24.47], rj['entity.MinecartChest.name'/2196, l='MpServer', x=335.50, y=17.85, z=44.50], qg['Bat'/2197, l='MpServer', x=255.03, y=12.03, z=0.75], qg['Bat'/2198, l='MpServer', x=255.84, y=16.64, z=-37.66], qn['Pig'/2199, l='MpServer', x=316.22, y=67.00, z=-92.47], qn['Pig'/2185, l='MpServer', x=331.66, y=66.00, z=-71.53], qn['Pig'/2184, l='MpServer', x=280.66, y=70.00, z=-24.19], qn['Pig'/2187, l='MpServer', x=324.06, y=68.00, z=-65.06], qn['Pig'/2186, l='MpServer', x=332.66, y=66.00, z=-69.80], qn['Pig'/2189, l='MpServer', x=336.16, y=65.00, z=-71.00], qn['Pig'/2188, l='MpServer', x=309.81, y=66.00, z=-69.94], qn['Pig'/2191, l='MpServer', x=296.50, y=71.00, z=-65.69], qn['Pig'/2190, l='MpServer', x=286.81, y=72.00, z=-57.38], qn['Pig'/2181, l='MpServer', x=299.09, y=71.00, z=-38.97], rh['item.tile.lava'/2180, l='MpServer', x=331.72, y=87.13, z=-27.00], qn['Pig'/2183, l='MpServer', x=294.53, y=72.00, z=-62.63], qn['Pig'/2182, l='MpServer', x=344.84, y=71.00, z=-58.88], qn['Pig'/2226, l='MpServer', x=257.31, y=56.00, z=49.50], qn['Pig'/2213, l='MpServer', x=361.72, y=72.00, z=-100.03]]
Retry entities: 0 total; []
Stacktrace:
at bdt.a(SourceFile:282)
at net.minecraft.client.Minecraft.l(SourceFile:1332)
at net.minecraft.client.Minecraft.K(SourceFile:574)
at net.minecraft.client.Minecraft.run(SourceFile:526)
at java.lang.Thread.run(Unknown Source)

– Affected level –
Details:
Level name: MpServer
All players: 1 total; [bdw['McF4rtson'/2179, l='MpServer', x=326.99, y=88.62, z=-20.96]]
Chunk stats: MultiplayerChunkCache: 160
Level seed: 0
Level generator: ID 00 - default, ver 1. Features enabled: false
Level generator options:
Level spawn location: World: (0,64,0), Chunk: (at 0,4,0 in 0,0; contains blocks 0,0,0 to 15,255,15), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
Level time: 1711795 game time, 1711795 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: survival (ID 0). Hardcore: false. Cheats: false
Forced entities: 30 total; [bdw['McF4rtson'/2179, l='MpServer', x=326.99, y=88.62, z=-20.96], qn['Pig'/2200, l='MpServer', x=351.31, y=67.00, z=-88.50], rh['item.item.porkchopRaw'/2201, l='MpServer', x=377.78, y=67.13, z=-64.06], qn['Pig'/2202, l='MpServer', x=300.22, y=64.00, z=-95.84], qn['Pig'/2203, l='MpServer', x=352.06, y=65.00, z=-84.03], rj['entity.MinecartChest.name'/2205, l='MpServer', x=285.50, y=11.69, z=37.50], qg['Bat'/2206, l='MpServer', x=258.53, y=23.10, z=-75.91], qg['Bat'/2207, l='MpServer', x=265.56, y=40.10, z=-71.00], qn['Pig'/2192, l='MpServer', x=352.47, y=67.00, z=-70.31], qn['Pig'/2193, l='MpServer', x=376.19, y=67.00, z=-58.50], qg['Bat'/2194, l='MpServer', x=268.75, y=17.10, z=-26.25], qn['Pig'/2195, l='MpServer', x=261.31, y=63.00, z=-24.47], rj['entity.MinecartChest.name'/2196, l='MpServer', x=335.50, y=17.85, z=44.50], qg['Bat'/2197, l='MpServer', x=255.03, y=12.03, z=0.75], qg['Bat'/2198, l='MpServer', x=255.84, y=16.64, z=-37.66], qn['Pig'/2199, l='MpServer', x=316.22, y=67.00, z=-92.47], qn['Pig'/2185, l='MpServer', x=331.66, y=66.00, z=-71.53], qn['Pig'/2184, l='MpServer', x=280.66, y=70.00, z=-24.19], qn['Pig'/2187, l='MpServer', x=324.06, y=68.00, z=-65.06], qn['Pig'/2186, l='MpServer', x=332.66, y=66.00, z=-69.80], qn['Pig'/2189, l='MpServer', x=336.16, y=65.00, z=-71.00], qn['Pig'/2188, l='MpServer', x=309.81, y=66.00, z=-69.94], qn['Pig'/2191, l='MpServer', x=296.50, y=71.00, z=-65.69], qn['Pig'/2190, l='MpServer', x=286.81, y=72.00, z=-57.38], qn['Pig'/2181, l='MpServer', x=299.09, y=71.00, z=-38.97], rh['item.tile.lava'/2180, l='MpServer', x=331.72, y=87.13, z=-27.00], qn['Pig'/2183, l='MpServer', x=294.53, y=72.00, z=-62.63], qn['Pig'/2182, l='MpServer', x=344.84, y=71.00, z=-58.88], qn['Pig'/2226, l='MpServer', x=257.31, y=56.00, z=49.50], qn['Pig'/2213, l='MpServer', x=361.72, y=72.00, z=-100.03]]
Retry entities: 0 total; []

– System Details –
Details:
Minecraft Version: 1.5.1
Operating System: Windows 7 (amd64) version 6.1
Java Version: 1.7.0_09, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 375971280 bytes (358 MB) / 514523136 bytes (490 MB) up to 954466304 bytes (910 MB)
JVM Flags: 2 total; -Xms512m -Xmx1024m
AABB Pool Size: 8706 (487536 bytes; 0 MB) allocated, 438 (24528 bytes; 0 MB) used
Suspicious classes: No suspicious classes found.
IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
LWJGL: 2.4.2
OpenGL: AMD Radeon HD 7310M GL version 4.2.11399 Compatibility Profile Context, ATI Technologies Inc.
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: 1482 (82992 bytes; 0 MB) allocated, 66 (3696 bytes; 0 MB) used

java.lang.NullPointerException
at arj.b(SourceFile:210)
at bdl.a(SourceFile:1145)
at fd.a(SourceFile:99)
at ci.b(SourceFile:350)
at bdl.d(SourceFile:95)
at bdt.b(SourceFile:58)
at net.minecraft.client.Minecraft.l(SourceFile:1325)
at net.minecraft.client.Minecraft.K(SourceFile:574)
at net.minecraft.client.Minecraft.run(SourceFile:526)
at java.lang.Thread.run(Unknown Source)
— END ERROR REPORT be2a37 ----------

Here is the server IP, in case it needs to be tested: Removed IP address