error

2012-10-09 18:38:12 [WARNING] [Server] The main thread failed to respond after 10 seconds
2012-10-09 18:38:12 [WARNING] [Server] What follows is the stack trace of the main thread
2012-10-09 18:38:12 [WARNING] [Server]    at java.lang.Thread.sleep(Native Method)
2012-10-09 18:38:12 [WARNING] [Server]    at net.minecraft.server.FileIOThread.a(SourceFile:59)
2012-10-09 18:38:12 [WARNING] [Server]    at net.minecraft.server.ServerNBTManager.a(SourceFile:47)
2012-10-09 18:38:12 [WARNING] [Server]    at net.minecraft.server.WorldServer.saveLevel(WorldServer.java:819)
2012-10-09 18:38:12 [WARNING] [Server]    at net.minecraft.server.MinecraftServer.saveChunks(MinecraftServer.java:313)
2012-10-09 18:38:24 [WARNING] [Server] The main thread is still stuck, current loop line is:
2012-10-09 18:38:24 [WARNING] [Server]    at net.minecraft.server.FileIOThread.a(SourceFile:59)