I have a hamachi server that was working fine yesterday, but my dad tried to port forward. It said the port was closed, and he had to go out so he is having another look tonight. I (The host) can join the server fine but my friend (callum8346) cannot. I get this error in the console:

2012-04-12 10:34:37 [INFO] callum8346 [/5.1.109.66:2088] logged in with entity id 5366 at ([world] -202.911454911366, 71.0, 480.4046289255612)
2012-04-12 10:36:31 [SEVERE] java.net.SocketException: Socket closed
2012-04-12 10:36:31 [SEVERE] at java.net.SocketOutputStream.socketWrite(Unknown Source)
2012-04-12 10:36:31 [SEVERE] at java.net.SocketOutputStream.write(Unknown Source)
2012-04-12 10:36:31 [SEVERE] at java.io.BufferedOutputStream.flushBuffer(Unknown Source)
2012-04-12 10:36:31 [SEVERE] at java.io.BufferedOutputStream.flush(Unknown Source)
2012-04-12 10:36:31 [SEVERE] at java.io.DataOutputStream.flush(Unknown Source)
2012-04-12 10:36:31 [SEVERE] at net.minecraft.server.NetworkWriterThread.run(SourceFile:103)
2012-04-12 10:36:31 [INFO] callum8346 lost connection: disconnect.endOfStream

P.s. This is a bukkit server. Ask if you need a list of the plugins.