When I try to lunch fireworks - server (1.4.6 with diablo-jdk1.6) kicks me out. And I can't connect anymore.
I updated java to openjdk6, but still cant connect, see the log:

Starting Minecraft...
210 recipes
27 achievements
2012-12-23 13:43:56 [INFO] Starting minecraft server version 1.4.6
2012-12-23 13:43:56 [INFO] Loading properties
2012-12-23 13:43:56 [INFO] Default game type: SURVIVAL
2012-12-23 13:43:56 [INFO] Generating keypair
2012-12-23 13:43:57 [INFO] Starting Minecraft server on *:25565
2012-12-23 13:43:57 [WARNING] **** SERVER IS RUNNING IN OFFLINE/INSECURE MODE!
2012-12-23 13:43:57 [WARNING] The server will make no attempt to authenticate usernames. Beware.
2012-12-23 13:43:57 [WARNING] While this makes the game possible to play without internet access, it also opens up the ability for hackers to connect with any username they choose.
2012-12-23 13:43:57 [WARNING] To change this, set "online-mode" to "true" in the server.properties file.
2012-12-23 13:43:57 [INFO] Preparing level "world"
2012-12-23 13:43:57 [INFO] Preparing start region for level 0
2012-12-23 13:43:58 [INFO] Done (1,132s)! For help, type "help" or "?"
Invalid argument <- Client opens LAN games
Invalid argument <- Client try to connect
2012-12-23 13:44:03 [INFO] NikitaTratorov[/95.28.208.227:53318] logged in with entity id 27 at (-357.0897381757311, 64.0, -493.33058578735177)
java.lang.NullPointerException
at ef.a(SourceFile:310)
at mj.a(SourceFile:237)
at mj.a(SourceFile:157)
at et.a(SourceFile:36)
at ef.a(SourceFile:214)
at cg.h(SourceFile:178)
at cg.d(SourceFile:15)
at ci.run(SourceFile:114)
2012-12-23 13:44:04 [INFO] NikitaTratorov lost connection: disconnect.genericReason
stop
2012-12-23 13:48:57 [INFO] Stopping the server
2012-12-23 13:48:57 [INFO] Stopping server
2012-12-23 13:48:57 [INFO] Saving players
java.net.SocketException: Socket closed
at java.net.PlainSocketImpl.socketAccept(Native Method)
at java.net.AbstractPlainSocketImpl.accept(AbstractPlainSocketImpl.java:375)
at java.net.ServerSocket.implAccept(ServerSocket.java:470)
at java.net.ServerSocket.accept(ServerSocket.java:438)
at hu.run(SourceFile:66)
Closing listening thread2012-12-23 13:48:57 [INFO] Saving worlds

2012-12-23 13:48:57 [INFO] Saving chunks for level 'world'/Overworld
2012-12-23 13:48:57 [INFO] Saving chunks for level 'world'/Nether
2012-12-23 13:48:57 [INFO] Saving chunks for level 'world'/The End