Players get blue/black screen, not able to chat.

Players clients will crash. When they try to log back on, all they can see is a blue screen, not the sky, simply a light blue screen, they can't use chat either, also you have to use Task Manager to end the java process!

This is not a client problem, it's been happening to MANY of the players on my server. Here is the error code that appears in the console.

Code:

2011-08-03 15:41:13 [SEVERE] java.io.IOException: Bad packet id 81
2011-08-03 15:41:13 [SEVERE]     at net.minecraft.server.Packet.a(Packet.java:73)
2011-08-03 15:41:13 [SEVERE]     at net.minecraft.server.NetworkManager.g(NetworkManager.java:149)
2011-08-03 15:41:13 [SEVERE]     at net.minecraft.server.NetworkManager.c(NetworkManager.java:259)
2011-08-03 15:41:13 [SEVERE]     at net.minecraft.server.NetworkReaderThread.run(SourceFile:84)
2011-08-03 15:41:13 [INFO] /XXX.XXX.XX.XXX:40051 lost connection
2011-08-03 15:41:18 [SEVERE] java.io.IOException: Bad packet id 81
2011-08-03 15:41:18 [SEVERE]     at net.minecraft.server.Packet.a(Packet.java:73)
2011-08-03 15:41:18 [SEVERE]     at net.minecraft.server.NetworkManager.g(NetworkManager.java:149)
2011-08-03 15:41:18 [SEVERE]     at net.minecraft.server.NetworkManager.c(NetworkManager.java:259)
2011-08-03 15:41:18 [SEVERE]     at net.minecraft.server.NetworkReaderThread.run(SourceFile:84)
2011-08-03 15:41:18 [INFO] /XXX.XXX.XX.XXX:40097 lost connection

If anyone can help, please feel free to - I need it!

 

This makes me think that a common client mod is being used....


PS Uhh why hide the IPs? You do know that EVERY interaction on the internet will show the IPs?

 

The only mods I use are X-Ray, Zombie Mod (Fly), and Optimine+Optifog,
But I've verified that players aren't using these.
And I am sure it's not this since I have to remove their player.dat file or teleport them to out spawn area when they log on.

 

Are they trying to spawn items with the value of -1 ?

That can mess with a users .dat and cause it so they cant log in.

 

No - Spawning items isn't allowed, our server is survival/vanilla based. It has something to do with the chunks I guarantee, because one guy got the glitch and he re-opened MC and it worked fine, don't know why it "stays" with certain people.

I've checked some stuff out and read this:

I forced update to have a clear minecraft.jar - I still get the crashes.
They are completely random and it happens to others on my server. One guy was simply chopping a tree and it started it.

EDIT by Moderator: merged posts, please use the edit button instead of double posting.

 

Chopping trees, eh? Sounds like you might have ChopTree installed?