Minecraft crashes when I try to load any SSP world.

Minecraft crashes when I attempt to load any survival/creative singleplayer world.

Minecraft works normally on survival/creative multiplayer.

Yes, I use mods, even if these reports say I don't. It still crashes without the mods I use, which are these: (all of them latest version) ModLoader, Optifine, Autoswitcher, TooManyItems, and thebombzen's API mod.

How do you reproduce this problem?

1. Open Minecraft
2. Choose any survival/creative singeplayer world.
3. Attempt to open the world so you can play it.
4. Get an error/crash report screen.

I use 32 bit Windows XP Home Edition Service Pack 3.
Minecraft version 1.4.5

Here's the last 3 crash reports I got. Yes, this is happening over and over and over....

Crash Report #1

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

Time: 12/9/12 6:31 PM
Description: Rendering screen

java.lang.RuntimeException: Failed to check session lock, aborting
at aho.h(SourceFile:49)
at aho.<init>(SourceFile:35)
at ahk.<init>(SourceFile:16)
at ahl.a(SourceFile:78)
at net.minecraft.client.Minecraft.a(SourceFile:1369)
at auh.e(SourceFile:157)
at aui.a(SourceFile:205)
at aug.a(SourceFile:175)
at auh.a(SourceFile:178)
at bac.b(SourceFile:774)
at net.minecraft.client.Minecraft.J(SourceFile:604)
at net.minecraft.client.Minecraft.run(SourceFile:534)
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 aho.h(SourceFile:49)
at aho.<init>(SourceFile:35)
at ahk.<init>(SourceFile:16)
at ahl.a(SourceFile:78)
at net.minecraft.client.Minecraft.a(SourceFile:1369)
at auh.e(SourceFile:157)
at aui.a(SourceFile:205)
at aug.a(SourceFile:175)
at auh.a(SourceFile:178)

-- Screen render details --
Details:
Screen name: bem
Mouse location: Scaled: (164, 115). Absolute: (329, 248)
Screen size: Scaled: (427, 240). Absolute: (854, 480). Scale factor of 2
Stacktrace:
at bac.b(SourceFile:774)
at net.minecraft.client.Minecraft.J(SourceFile:604)
at net.minecraft.client.Minecraft.run(SourceFile:534)
at java.lang.Thread.run(Unknown Source)

-- System Details --
Details:
Minecraft Version: 1.4.5
Operating System: Windows XP (x86) version 5.1
Java Version: 1.7.0_09, Oracle Corporation
Java VM Version: Java HotSpot™ Client VM (mixed mode), Oracle Corporation
Memory: 453233632 bytes (432 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: 0, tallocated: 0
LWJGL: 2.4.2
OpenGL: GeForce 8200/PCI/SSE2/3DNOW! GL version 3.0.0, NVIDIA Corporation
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

Crash Report #2

---- Minecraft Crash Report ----
// I bet Cylons wouldn't have this problem.

Time: 12/9/12 6:37 PM
Description: Updating screen events

java.lang.RuntimeException: Failed to check session lock, aborting
at aho.h(SourceFile:49)
at aho.<init>(SourceFile:35)
at ahk.<init>(SourceFile:16)
at ahl.a(SourceFile:78)
at net.minecraft.client.Minecraft.a(SourceFile:1369)
at auh.e(SourceFile:157)
at auh.a(SourceFile:122)
at aue.a(SourceFile:71)
at aue.d(SourceFile:125)
at aue.m(SourceFile:110)
at net.minecraft.client.Minecraft.l(SourceFile:1085)
at net.minecraft.client.Minecraft.J(SourceFile:582)
at net.minecraft.client.Minecraft.run(SourceFile:534)
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 aho.h(SourceFile:49)
at aho.<init>(SourceFile:35)
at ahk.<init>(SourceFile:16)
at ahl.a(SourceFile:78)
at net.minecraft.client.Minecraft.a(SourceFile:1369)
at auh.e(SourceFile:157)
at auh.a(SourceFile:122)
at aue.a(SourceFile:71)
at aue.d(SourceFile:125)
at aue.m(SourceFile:110)

-- Affected screen --
Details:
Screen name: bem
Stacktrace:
at net.minecraft.client.Minecraft.l(SourceFile:1085)
at net.minecraft.client.Minecraft.J(SourceFile:582)
at net.minecraft.client.Minecraft.run(SourceFile:534)
at java.lang.Thread.run(Unknown Source)

-- System Details --
Details:
Minecraft Version: 1.4.5
Operating System: Windows XP (x86) version 5.1
Java Version: 1.7.0_09, Oracle Corporation
Java VM Version: Java HotSpot™ Client VM (mixed mode), Oracle Corporation
Memory: 469470928 bytes (447 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: IWrUpdater, Config, WrUpdaterSmooth, ...]
IntCache: cache: 0, tcache: 0, allocated: 3, tallocated: 63
ModLoader: Mods loaded: 4
ModLoader 1.4.5
mod_ThebombzenAPI ThebombzenAPI v1.1.4 for Minecraft 1.4.5
mod_AutoSwitch AutoSwitch v2.4.8 for Minecraft 1.4.5
mod_TooManyItems 1.4.5 2012-11-19

LWJGL: 2.4.2
OpenGL: GeForce 8200/PCI/SSE2/3DNOW! GL version 3.0.0, NVIDIA Corporation
Is Modded: Very likely; Jar signature invalidated
Type: Client (map_client.txt)
Texture Pack: Default
Profiler Position: N/A (disabled)
Vec3 Pool Size: ~~ERROR~~ NullPointerException: null

Crash Report #3

---- Minecraft Crash Report ----
// I just don't know what went wrong :(

Time: 12/9/12 6:47 PM
Description: Rendering screen

java.lang.RuntimeException: Failed to check session lock, aborting
at aho.h(SourceFile:49)
at aho.<init>(SourceFile:35)
at ahk.<init>(SourceFile:16)
at ahl.a(SourceFile:78)
at net.minecraft.client.Minecraft.a(SourceFile:1369)
at auh.e(SourceFile:157)
at aui.a(SourceFile:205)
at aug.a(SourceFile:175)
at auh.a(SourceFile:178)
at bac.b(EntityRenderer.java:1147)
at EntityRendererProxy.b(EntityRendererProxy.java:20)
at net.minecraft.client.Minecraft.J(SourceFile:604)
at net.minecraft.client.Minecraft.run(SourceFile:534)
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 aho.h(SourceFile:49)
at aho.<init>(SourceFile:35)
at ahk.<init>(SourceFile:16)
at ahl.a(SourceFile:78)
at net.minecraft.client.Minecraft.a(SourceFile:1369)
at auh.e(SourceFile:157)
at aui.a(SourceFile:205)
at aug.a(SourceFile:175)
at auh.a(SourceFile:178)

-- Screen render details --
Details:
Screen name: bem
Mouse location: Scaled: (149, 43). Absolute: (299, 393)
Screen size: Scaled: (427, 240). Absolute: (854, 480). Scale factor of 2
Stacktrace:
at bac.b(EntityRenderer.java:1147)
at EntityRendererProxy.b(EntityRendererProxy.java:20)
at net.minecraft.client.Minecraft.J(SourceFile:604)
at net.minecraft.client.Minecraft.run(SourceFile:534)
at java.lang.Thread.run(Unknown Source)

-- System Details --
Details:
Minecraft Version: 1.4.5
Operating System: Windows XP (x86) version 5.1
Java Version: 1.7.0_09, Oracle Corporation
Java VM Version: Java HotSpot™ Client VM (mixed mode), Oracle Corporation
Memory: 476206576 bytes (454 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: IWrUpdater, Config, WrUpdaterSmooth, ...]
IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
ModLoader: Mods loaded: 4
ModLoader 1.4.5
mod_ThebombzenAPI ThebombzenAPI v1.1.4 for Minecraft 1.4.5
mod_AutoSwitch AutoSwitch v2.4.8 for Minecraft 1.4.5
mod_TooManyItems 1.4.5 2012-11-19

LWJGL: 2.4.2
OpenGL: GeForce 8200/PCI/SSE2/3DNOW! GL version 3.0.0, NVIDIA Corporation
Is Modded: Very likely; Jar signature invalidated
Type: Client (map_client.txt)
Texture Pack: Default
Profiler Position: N/A (disabled)
Vec3 Pool Size: ~~ERROR~~ NullPointerException: null