java.net.SocketException: Socket closed

Hello, I have a problem becouse after my Minecraft 1.1 server running for 4-5 hours, I get an error like this:

2012-02-11 15:17:12 [INFO] Biox33 lost connection: disconnect.quitting
2012-02-11 15:17:12 [SEVERE] java.net.SocketException: Socket closed
2012-02-11 15:17:12 [SEVERE] at java.net.SocketOutputStream.socketWrite(Unknown Source)
2012-02-11 15:17:12 [SEVERE] at java.net.SocketOutputStream.write(Unknown Source)
2012-02-11 15:17:12 [SEVERE] at java.io.BufferedOutputStream.flushBuffer(Unknown Source)
2012-02-11 15:17:12 [SEVERE] at java.io.BufferedOutputStream.flush(Unknown Source)
2012-02-11 15:17:12 [SEVERE] at java.io.DataOutputStream.flush(Unknown Source)
2012-02-11 15:17:12 [SEVERE] at net.minecraft.server.NetworkWriterThread.run(SourceFile:103)

It usually happens after a player disconnected, but not all time, only 4-5 hours after server started or this message appears. My server get freezed for 10-15 seconds, and it drops down 5-10 players from my server. Anybody know any solution for this?