Minecraft: Ayuda server bukkit

Bueno pues cuando inicio el server me pone:  FAILED TO BIND TO PORT
y luego me pone :  the exception was: java.net.bindexception:cannot assing... y otras cosas

y abajo de todo me pone: perhaps a server is already running on that port?


porque me pone eso??? saben de que puede ser??
muchas gracias  

edito,para los que sepan este es el crash report:
---- Minecraft Crash Report ----
// You should try our sister game, Minceraft!

Time: 16/07/13 12:39
Description: Exception in server tick loop

java.lang.NullPointerException
	at net.minecraft.server.v1_5_R3.DedicatedServer.an(DedicatedServer.java:258)
	at net.minecraft.server.v1_5_R3.DedicatedServer.a(DedicatedServer.java:204)
	at net.minecraft.server.v1_5_R3.MinecraftServer.run(MinecraftServer.java:417)
	at net.minecraft.server.v1_5_R3.ThreadServerApplication.run(SourceFile:573)


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

-- System Details --
Details:
	Minecraft Version: 1.5.2
	Operating System: Windows 7 (x86) version 6.1
	Java Version: 1.7.0_25, Oracle Corporation
	Java VM Version: Java HotSpot(TM) Client VM (mixed mode), Oracle Corporation
	Memory: 986414792 bytes (940 MB) / 1037959168 bytes (989 MB) up to 1037959168 bytes (989 MB)
	JVM Flags: 2 total; -Xms1024M -Xmx1024M
	AABB Pool Size: 0 (0 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
	Suspicious classes: [net.minecraft.server.v1_5_R3.ICommandListener, IMojangStatistics, IDataManager, ...], [org.bukkit.World, BlockChangeDelegate, Server], [org.bukkit.block.BlockState], [org.bukkit.command.CommandSender, RemoteConsoleCommandSender], [org.bukkit.configuration.serialization.ConfigurationSerializable], [org.bukkit.craftbukkit.Main], [org.bukkit.craftbukkit.libs.jline.TerminalFactory, Terminal, Flavor, ...], [org.bukkit.craftbukkit.libs.jline.console.ConsoleReader, CursorBuffer, ConsoleKeys, ...], [org.bukkit.craftbukkit.libs.jline.console.completer.CompletionHandler, CandidateListCompletionHandler], [org.bukkit.craftbukkit.libs.jline.console.history.History, MemoryHistory], [org.bukkit.craftbukkit.libs.jline.internal.InputStreamReader, Configuration, Log], [org.bukkit.craftbukkit.libs.joptsimple.OptionException, OptionParser, OptionSpec, ...], [org.bukkit.craftbukkit.libs.joptsimple.internal.AbbreviationMap, ReflectionException, Reflection, ...], [org.bukkit.craftbukkit.v1_5_R3.LoggerOutputStream, CraftServer], [org.bukkit.craftbukkit.v1_5_R3.inventory.CraftItemStack, CraftInventory, CraftInventoryDoubleChest, ...], [org.bukkit.craftbukkit.v1_5_R3.potion.CraftPotionEffectType], [org.bukkit.craftbukkit.v1_5_R3.util.Waitable, ServerShutdownThread, TerminalConsoleHandler, ...], [org.bukkit.entity.Entity], [org.bukkit.event.Event, Cancellable, HandlerList, ...], [org.bukkit.event.block.BlockEvent, BlockFadeEvent, BlockGrowEvent, ...], [org.bukkit.event.entity.EntityEvent, EntityInteractEvent, EntityDamageEvent, ...], [org.bukkit.event.hanging.HangingEvent, HangingPlaceEvent], [org.bukkit.event.inventory.InventoryMoveItemEvent], [org.bukkit.event.painting.PaintingEvent, PaintingPlaceEvent], [org.bukkit.event.player.PlayerEvent, PlayerInteractEvent, PlayerFishEvent], [org.bukkit.event.server.ServerEvent, MapInitializeEvent, ServerCommandEvent], [org.bukkit.event.world.WorldEvent, WorldSaveEvent, WorldInitEvent, ...], [org.bukkit.inventory.ItemStack, Inventory, DoubleChestInventory, ...], [org.bukkit.map.MapView], [org.bukkit.metadata.Metadatable], [org.bukkit.permissions.ServerOperator, Permissible], [org.bukkit.plugin.messaging.PluginMessageRecipient], [org.bukkit.potion.PotionEffectType, PotionEffectTypeWrapper], [org.fusesource.hawtjni.runtime.Library], [org.fusesource.jansi.AnsiOutputStream, WindowsAnsiOutputStream, AnsiConsole, ...], [org.fusesource.jansi.internal.Kernel32, CONSOLE_SCREEN_BUFFER_INFO, COORD, ...]
	IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
	CraftBukkit Information: 
   Running: 
   Failed to handle CraftCrashReport:
java.lang.NullPointerException
	at org.bukkit.Bukkit.getName(Bukkit.java:72)
	at org.bukkit.craftbukkit.v1_5_R3.CraftCrashReport.call(CraftCrashReport.java:20)
	at net.minecraft.server.v1_5_R3.CrashReportSystemDetails.a(SourceFile:74)
	at net.minecraft.server.v1_5_R3.CrashReport.h(CrashReport.java:41)
	at net.minecraft.server.v1_5_R3.CrashReport.(CrashReport.java:28)
	at net.minecraft.server.v1_5_R3.MinecraftServer.run(MinecraftServer.java:427)
	at net.minecraft.server.v1_5_R3.ThreadServerApplication.run(SourceFile:573)

	Profiler Position: N/A (disabled)
	Is Modded: Definitely; Server brand changed to 'craftbukkit'
	Type: Dedicated Server (map_server.txt)
EDITADO EL 16-07-2013 / 13:42 (EDITADO 1 VEZ)