12:50:22 AM [SEVERE] net.minecraft.server.v1_5_R3.ExceptionWorldConflict: Failed to check session lock, aborting
12:50:22 AM [SEVERE] 	at net.minecraft.server.v1_5_R3.WorldNBTStorage.checkSession(WorldNBTStorage.java:75)
12:50:22 AM [SEVERE] 	at net.minecraft.server.v1_5_R3.World.F(World.java:2599)
12:50:22 AM [SEVERE] 	at net.minecraft.server.v1_5_R3.ChunkRegionLoader.a(ChunkRegionLoader.java:129)
12:50:22 AM [SEVERE] 	at net.minecraft.server.v1_5_R3.ChunkProviderServer.saveChunk(ChunkProviderServer.java:207)
12:50:22 AM [SEVERE] 	at net.minecraft.server.v1_5_R3.ChunkProviderServer.unloadChunks(ChunkProviderServer.java:295)
12:50:22 AM [SEVERE] 	at net.minecraft.server.v1_5_R3.WorldServer.doTick(WorldServer.java:190)
12:50:22 AM [SEVERE] 	at net.minecraft.server.v1_5_R3.MinecraftServer.r(MinecraftServer.java:555)
12:50:22 AM [SEVERE] 	at net.minecraft.server.v1_5_R3.DedicatedServer.r(DedicatedServer.java:226)
12:50:22 AM [SEVERE] 	at net.minecraft.server.v1_5_R3.MinecraftServer.q(MinecraftServer.java:477)
12:50:23 AM [SEVERE] 	at net.minecraft.server.v1_5_R3.MinecraftServer.run(MinecraftServer.java:410)
12:50:23 AM [SEVERE] 	at net.minecraft.server.v1_5_R3.ThreadServerApplication.run(SourceFile:573)