If you using HyperVM and get this error message after upgrading your dom0’s Xen kernel:
iptables v1.2.11: can't initialize iptables table `filter': iptables who? (do you need to insmod?)
Perhaps iptables or your kernel needs to be upgraded.
It means that the library for the kernel is not copied yet to the VM. To fix this simply copy the new kernel library from /lib/modules/<new kernel> to VM’s /lib/modules directory then restart the VM.