No one can connect to the server

[Derrick Bowman]

Installed Tekkit 2.1.1 for the server and the clients are running the recommend build, 3.0.3

When someone connects, this is what I see -

2012-06-08 15:30:03 [sEVERE] java.io.IOException: Received string length longer than maximum allowed (107 > 16)

2012-06-08 15:30:03 [sEVERE] at net.minecraft.server.Packet.a(Packet.java:120)

2012-06-08 15:30:03 [sEVERE] at net.minecraft.server.Packet.a(Packet.java:120)

2012-06-08 15:30:03 [sEVERE] at net.minecraft.server.Packet1Login.a(Packet1Login.java:38)

2012-06-08 15:30:03 [sEVERE] at net.minecraft.server.Packet.a(Packet.java:79)

2012-06-08 15:30:03 [sEVERE] at net.minecraft.server.NetworkManager.h(NetworkManager.java:152)

2012-06-08 15:30:03 [sEVERE] at net.minecraft.server.NetworkManager.c(NetworkManager.java:270)

2012-06-08 15:30:03 [sEVERE] at net.minecraft.server.NetworkReaderThread.run(SourceFile:76)

I have java updated, but could this be server side issue with java being outdated? I found posts like this for MAC, but nothing for Windows.

[Yuriy]

Installed Tekkit 2.1.1 for the server and the clients are running the recommend build, 3.0.3

...

Seek help for your severe mental deficiency.

They're for different MC versions and, obviously, one doesn't connect to the other.