My computer suddenly turned off while playing Minecraft, and when I tried to start my game again, I failed.

I forgot, sorry:
---- Minecraft Crash Report ----
// You're mean.

Time: 17.07.13 10:26
Description: Exception in server tick loop

java.util.ConcurrentModificationException
at java.util.HashMap$HashIterator.nextEntry(Unknown Source)
at java.util.HashMap$ValueIterator.next(Unknown Source)
at aim.a(SourceFile:69)
at aes.a(SourceFile:425)
at jq.a(SourceFile:168)
at adq.a(SourceFile:732)
at jq.c(SourceFile:105)
at jp.<init>(SourceFile:29)
at jo.a(SourceFile:208)
at jo.a(SourceFile:240)
at hm.a(SourceFile:141)
at hm.c(SourceFile:188)
at hm.a(SourceFile:85)
at bkz.b(SourceFile:73)
at net.minecraft.server.MinecraftServer.t(SourceFile:488)
at net.minecraft.server.MinecraftServer.s(SourceFile:405)
at bkw.s(SourceFile:124)
at net.minecraft.server.MinecraftServer.run(SourceFile:339)
at hh.run(SourceFile:582)

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

– System Details –
Details:
Minecraft Version: 1.6.2
Operating System: Windows XP (x86) version 5.1
Java Version: 1.7.0_25, Oracle Corporation
Java VM Version: Java HotSpot(TM) Client VM (mixed mode, sharing), Oracle Corporation
Memory: 92609016 bytes (88 MB) / 206589952 bytes (197 MB) up to 518979584 bytes (494 MB)
JVM Flags: 1 total; -Xmx512M
AABB Pool Size: 3514 (196784 bytes; 0 MB) allocated, 3514 (196784 bytes; 0 MB) used
Suspicious classes: No suspicious classes found.
IntCache: cache: 0, tcache: 0, allocated: 3, tallocated: 63
Profiler Position: N/A (disabled)
Vec3 Pool Size: 428 (23968 bytes; 0 MB) allocated, 428 (23968 bytes; 0 MB) used
Player Count: 1 / 8; [ju['Alyson_Spyral'/297, l='wORLD', x=730,70, y=65,00, z=303,01]]
Type: Integrated Server (map_client.txt)
Is Modded: Probably not. Jar signature remains and both client + server brands are untouche