This crash deleted my friends level.dat and <player>.dat

As this isn't in the changelog, i assume this affects 1.7.4 to, but i'm not tagging it(yet!)
This is a crash that deleted my friends save(restored by making a new world with the exact same name, but all inventory was gone).

---- Minecraft Crash Report ----
// There are four lights!

Time: 12/8/13 11:38 PM
Description: Ticking memory connection

java.lang.IllegalStateException: Failed to add player. mp['Skootir'/165, l='Earth', x=162.30, y=63.00, z=632.03] already is in chunk 5, 34
at mk.a(SourceFile:37)
at mj.d(SourceFile:346)
at lg.d(SourceFile:215)
at na.a(SourceFile:280)
at iu.a(SourceFile:137)
at iw.a(SourceFile:20)
at ef.a(SourceFile:164)
at mv.c(SourceFile:134)
at net.minecraft.server.MinecraftServer.u(SourceFile:528)
at net.minecraft.server.MinecraftServer.t(SourceFile:440)
at btk.t(SourceFile:117)
at net.minecraft.server.MinecraftServer.run(SourceFile:357)
at lb.run(SourceFile:616)

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

– Head –
Stacktrace:
at mk.a(SourceFile:37)
at mj.d(SourceFile:346)
at lg.d(SourceFile:215)
at na.a(SourceFile:280)
at iu.a(SourceFile:137)
at iw.a(SourceFile:20)
at ef.a(SourceFile:164)

– Ticking connection –
Details:
Connection: ef@11e34c7
Stacktrace:
at mv.c(SourceFile:134)
at net.minecraft.server.MinecraftServer.u(SourceFile:528)
at net.minecraft.server.MinecraftServer.t(SourceFile:440)
at btk.t(SourceFile:117)
at net.minecraft.server.MinecraftServer.run(SourceFile:357)
at lb.run(SourceFile:616)

– System Details –
Details:
Minecraft Version: 1.7.3
Operating System: Windows 8 (x86) version 6.2
Java Version: 1.7.0_40, Oracle Corporation
Java VM Version: Java HotSpot(TM) Client VM (mixed mode, sharing), Oracle Corporation
Memory: 97622968 bytes (93 MB) / 518979584 bytes (494 MB) up to 518979584 bytes (494 MB)
JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx512M
AABB Pool Size: 5619 (314664 bytes; 0 MB) allocated, 832 (46592 bytes; 0 MB) used
IntCache: cache: 0, tcache: 0, allocated: 12, tallocated: 94
Profiler Position: N/A (disabled)
Vec3 Pool Size: 1199 (67144 bytes; 0 MB) allocated, 97 (5432 bytes; 0 MB) used
Player Count: 1 / 8; [mp['Skootir'/165, l='Earth', x=162.30, y=63.00, z=632.03]]
Type: Integrated Server (map_client.txt)
Is Modded: Probably not. Jar signature remains and both client + server brands are untouched.