iptables wrong version?

[Philip Mak <pmak@aaanime.net>]

I am trying to ban an IP address from my server (*.*.*.* is a real
IP):

[root@naga root]# ipchains -A INPUT --source *.*.*.* -p tcp -j DROP
ipchains: Protocol not available
[root@naga root]# iptables -A INPUT --source *.*.*.* -p tcp -j DROP       
iptables v1.2.11: can't initialize iptables table `filter': Module is wrong version
Perhaps iptables or your kernel needs to be upgraded.
[root@naga root]# uname -a
Linux naga.aaanime.net 2.6.8-11-amd64-k8 #1 Sun Oct 2 21:26:54 UTC 2005 x86_64 GNU/Linux
[root@naga root]# apt-get install iptables
Reading Package Lists... Done
Building Dependency Tree... Done
iptables is already the newest version.
0 upgraded, 0 newly installed, 0 to remove and 7 not upgraded.

Does anyone know what I'm doing wrong?