2012-01-22 18:48:20 [SEVERE] net.minecraft.server.WorldConlictException: Failed to check session lock, aborting
2012-01-22 18:48:20 [SEVERE] 	at net.minecraft.server.WorldNBTStorage.checkSession(WorldNBTStorage.java:74)
2012-01-22 18:48:20 [SEVERE] 	at net.minecraft.server.World.l(World.java:2653)
2012-01-22 18:48:20 [SEVERE] 	at net.minecraft.server.ChunkRegionLoader.a(SourceFile:78)
2012-01-22 18:48:20 [SEVERE] 	at net.minecraft.server.ChunkProviderServer.saveChunk(ChunkProviderServer.java:163)
2012-01-22 18:48:20 [SEVERE] 	at net.minecraft.server.ChunkProviderServer.unloadChunks(ChunkProviderServer.java:247)
2012-01-22 18:48:20 [SEVERE] 	at net.minecraft.server.World.doTick(World.java:1728)
2012-01-22 18:48:20 [SEVERE] 	at net.minecraft.server.MinecraftServer.w(MinecraftServer.java:523)
2012-01-22 18:48:20 [SEVERE] 	at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:434)
2012-01-22 18:48:20 [SEVERE] 	at net.minecraft.server.ThreadServerApplication.run(SourceFile:465)