Not in GZIP format, ChunkProviderServer.* and NullPointerException errors

Could someone please help me fix these errors? I can't start the server at all with these errors.

CraftBukkit build 1240.

Code:

2011-10-19 15:50:07 [INFO] Starting minecraft server version Beta 1.8.1
2011-10-19 15:50:07 [INFO] Loading properties
2011-10-19 15:50:07 [INFO] Starting Minecraft server on *:1337
2011-10-19 15:50:07 [INFO] This server is running Craftbukkit version git-Bukkit-0.0.0-1112-g54a13b2-b1240jnks (MC: 1.8.1)
2011-10-19 15:50:07 [INFO] [PermissionsEx] sql backend registered!
2011-10-19 15:50:07 [INFO] [PermissionsEx] file backend registered!
2011-10-19 15:50:07 [INFO] [PermissionsEx] PermissionEx plugin initialized.
2011-10-19 15:50:07 [INFO] [PermissionsEx] p2compat backend registered!
2011-10-19 15:50:07 [INFO] [PermissionsCompat] Compatibility Layer Initalized!
2011-10-19 15:50:07 [INFO] [PermissionsEx] Initializing file backend
2011-10-19 15:50:07 [INFO] Preparing level "Melons"
2011-10-19 15:50:07 [SEVERE] java.io.IOException: Not in GZIP format
2011-10-19 15:50:07 [SEVERE] 	at java.util.zip.GZIPInputStream.readHeader(Unknown Source)
2011-10-19 15:50:07 [SEVERE] 	at java.util.zip.GZIPInputStream.<init>(Unknown Source)
2011-10-19 15:50:07 [SEVERE] 	at java.util.zip.GZIPInputStream.<init>(Unknown Source)
2011-10-19 15:50:07 [SEVERE] 	at net.minecraft.server.CompressedStreamTools.a(SourceFile:9)
2011-10-19 15:50:07 [SEVERE] 	at net.minecraft.server.WorldLoader.b(SourceFile:50)
2011-10-19 15:50:07 [SEVERE] 	at net.minecraft.server.WorldLoaderServer.isConvertable(SourceFile:73)
2011-10-19 15:50:07 [SEVERE] 	at net.minecraft.server.MinecraftServer.a(MinecraftServer.java:169)
2011-10-19 15:50:07 [SEVERE] 	at net.minecraft.server.MinecraftServer.init(MinecraftServer.java:152)
2011-10-19 15:50:07 [SEVERE] 	at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:348)
2011-10-19 15:50:07 [SEVERE] 	at net.minecraft.server.ThreadServerApplication.run(SourceFile:417)
2011-10-19 15:50:07 [SEVERE] java.io.IOException: Not in GZIP format
2011-10-19 15:50:07 [SEVERE] 	at java.util.zip.GZIPInputStream.readHeader(Unknown Source)
2011-10-19 15:50:07 [SEVERE] 	at java.util.zip.GZIPInputStream.<init>(Unknown Source)
2011-10-19 15:50:07 [SEVERE] 	at java.util.zip.GZIPInputStream.<init>(Unknown Source)
2011-10-19 15:50:07 [SEVERE] 	at net.minecraft.server.CompressedStreamTools.a(SourceFile:9)
2011-10-19 15:50:07 [SEVERE] 	at net.minecraft.server.WorldLoader.b(SourceFile:61)
2011-10-19 15:50:07 [SEVERE] 	at net.minecraft.server.WorldLoaderServer.isConvertable(SourceFile:73)
2011-10-19 15:50:07 [SEVERE] 	at net.minecraft.server.MinecraftServer.a(MinecraftServer.java:169)
2011-10-19 15:50:07 [SEVERE] 	at net.minecraft.server.MinecraftServer.init(MinecraftServer.java:152)
2011-10-19 15:50:07 [SEVERE] 	at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:348)
2011-10-19 15:50:07 [SEVERE] 	at net.minecraft.server.ThreadServerApplication.run(SourceFile:417)
2011-10-19 15:50:07 [INFO] Default game type: 0
2011-10-19 15:50:07 [SEVERE] java.io.IOException: Not in GZIP format
2011-10-19 15:50:07 [SEVERE] 	at java.util.zip.GZIPInputStream.readHeader(Unknown Source)
2011-10-19 15:50:07 [SEVERE] 	at java.util.zip.GZIPInputStream.<init>(Unknown Source)
2011-10-19 15:50:07 [SEVERE] 	at java.util.zip.GZIPInputStream.<init>(Unknown Source)
2011-10-19 15:50:07 [SEVERE] 	at net.minecraft.server.CompressedStreamTools.a(SourceFile:9)
2011-10-19 15:50:07 [SEVERE] 	at net.minecraft.server.PlayerNBTManager.c(PlayerNBTManager.java:93)
2011-10-19 15:50:07 [SEVERE] 	at net.minecraft.server.World.<init>(World.java:128)
2011-10-19 15:50:07 [SEVERE] 	at net.minecraft.server.WorldServer.<init>(WorldServer.java:27)
2011-10-19 15:50:07 [SEVERE] 	at net.minecraft.server.MinecraftServer.a(MinecraftServer.java:191)
2011-10-19 15:50:07 [SEVERE] 	at net.minecraft.server.MinecraftServer.init(MinecraftServer.java:152)
2011-10-19 15:50:07 [SEVERE] 	at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:348)
2011-10-19 15:50:07 [SEVERE] 	at net.minecraft.server.ThreadServerApplication.run(SourceFile:417)
2011-10-19 15:50:07 [SEVERE] java.io.IOException: Not in GZIP format
2011-10-19 15:50:07 [SEVERE] 	at java.util.zip.GZIPInputStream.readHeader(Unknown Source)
2011-10-19 15:50:07 [SEVERE] 	at java.util.zip.GZIPInputStream.<init>(Unknown Source)
2011-10-19 15:50:07 [SEVERE] 	at java.util.zip.GZIPInputStream.<init>(Unknown Source)
2011-10-19 15:50:07 [SEVERE] 	at net.minecraft.server.CompressedStreamTools.a(SourceFile:9)
2011-10-19 15:50:07 [SEVERE] 	at net.minecraft.server.PlayerNBTManager.c(PlayerNBTManager.java:104)
2011-10-19 15:50:07 [SEVERE] 	at net.minecraft.server.World.<init>(World.java:128)
2011-10-19 15:50:07 [SEVERE] 	at net.minecraft.server.WorldServer.<init>(WorldServer.java:27)
2011-10-19 15:50:07 [SEVERE] 	at net.minecraft.server.MinecraftServer.a(MinecraftServer.java:191)
2011-10-19 15:50:07 [SEVERE] 	at net.minecraft.server.MinecraftServer.init(MinecraftServer.java:152)
2011-10-19 15:50:07 [SEVERE] 	at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:348)
2011-10-19 15:50:07 [SEVERE] 	at net.minecraft.server.ThreadServerApplication.run(SourceFile:417)
2011-10-19 15:50:07 [INFO] New max size: 400
2011-10-19 15:50:07 [INFO] New max size: 784
2011-10-19 15:50:07 [INFO] New max size: 1764
2011-10-19 15:50:07 [INFO] New max size: 5476
2011-10-19 15:50:07 [INFO] New max size: 18496
2011-10-19 15:50:07 [INFO] New max size: 19044
2011-10-19 15:50:07 [SEVERE] java.lang.NullPointerException
2011-10-19 15:50:07 [SEVERE] 	at net.minecraft.server.WorldServer.c(WorldServer.java:162)
2011-10-19 15:50:07 [SEVERE] 	at net.minecraft.server.World.a(World.java:2224)
2011-10-19 15:50:07 [SEVERE] 	at net.minecraft.server.Chunk.addEntities(Chunk.java:632)
2011-10-19 15:50:07 [SEVERE] 	at net.minecraft.server.ChunkProviderServer.getChunkAt(ChunkProviderServer.java:81)
2011-10-19 15:50:07 [SEVERE] 	at net.minecraft.server.ChunkProviderServer.getOrCreateChunk(ChunkProviderServer.java:106)
2011-10-19 15:50:07 [SEVERE] 	at net.minecraft.server.World.getChunkAt(World.java:300)
2011-10-19 15:50:07 [SEVERE] 	at net.minecraft.server.World.getTypeId(World.java:247)
2011-10-19 15:50:07 [SEVERE] 	at net.minecraft.server.World.isEmpty(World.java:251)
2011-10-19 15:50:07 [SEVERE] 	at net.minecraft.server.World.a(World.java:218)
2011-10-19 15:50:07 [SEVERE] 	at net.minecraft.server.WorldProvider.canSpawn(SourceFile:50)
2011-10-19 15:50:07 [SEVERE] 	at net.minecraft.server.World.canSpawn(World.java:104)
2011-10-19 15:50:07 [SEVERE] 	at net.minecraft.server.World.c(World.java:202)
2011-10-19 15:50:07 [SEVERE] 	at net.minecraft.server.World.<init>(World.java:150)
2011-10-19 15:50:07 [SEVERE] 	at net.minecraft.server.WorldServer.<init>(WorldServer.java:27)
2011-10-19 15:50:07 [SEVERE] 	at net.minecraft.server.MinecraftServer.a(MinecraftServer.java:191)
2011-10-19 15:50:07 [SEVERE] 	at net.minecraft.server.MinecraftServer.init(MinecraftServer.java:152)
2011-10-19 15:50:07 [SEVERE] 	at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:348)
2011-10-19 15:50:07 [SEVERE] 	at net.minecraft.server.ThreadServerApplication.run(SourceFile:417)
2011-10-19 15:50:07 [SEVERE] Unexpected exception
java.lang.NullPointerException
	at net.minecraft.server.WorldServer.c(WorldServer.java:162)
	at net.minecraft.server.World.a(World.java:2224)
	at net.minecraft.server.Chunk.addEntities(Chunk.java:632)
	at net.minecraft.server.ChunkProviderServer.getChunkAt(ChunkProviderServer.java:81)
	at net.minecraft.server.ChunkProviderServer.getOrCreateChunk(ChunkProviderServer.java:106)
	at net.minecraft.server.World.getChunkAt(World.java:300)
	at net.minecraft.server.World.getTypeId(World.java:247)
	at net.minecraft.server.World.isEmpty(World.java:251)
	at net.minecraft.server.World.a(World.java:218)
	at net.minecraft.server.WorldProvider.canSpawn(SourceFile:50)
	at net.minecraft.server.World.canSpawn(World.java:104)
	at net.minecraft.server.World.c(World.java:202)
	at net.minecraft.server.World.<init>(World.java:150)
	at net.minecraft.server.WorldServer.<init>(WorldServer.java:27)
	at net.minecraft.server.MinecraftServer.a(MinecraftServer.java:191)
	at net.minecraft.server.MinecraftServer.init(MinecraftServer.java:152)
	at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:348)
	at net.minecraft.server.ThreadServerApplication.run(SourceFile:417)

 

World is broken, download MCEdit, open the world & save it with that, or run Chunkster on it.

 

I actually had this same problem, and someone suggested I delete the world-nether folder, it actually worked, and now my server works again