According to the error the kernel module iptables_filter isn't loaded and OS can't load it for some reason. It could happen if:
1. You use custom kernel without iptables_filter support (Kernel installed from some 3rd party repository or compiled from sources with iptables_filter disabled)
2. Your provider uses OpenVZ/LXC virtualization and the kernel module iptables_filter isn't loaded at main node.
If the problem remains unsolved after the restoration then do following:
Run as root on your VPS:
uname -a
ls /lib/modules/$(uname -r)/kernel/net/ipv4/netfilter/
and show output.