Comment 12 for bug 1076050

I don't know the exact reason why ufw fails on your all's machines, so let's focus about the check-requirements script failure.

Fitzcarraldo, could you paste output of the command 'lsmod'?
Also, could you paste (or attach, preferred) kernel configuration matching CONFIG_NETFILTER and _NF_?
this should do, if you have config.gz:
zgrep CONFIG_NETFILTER /proc/config.gz
zgrep _NF_ /proc/config.gz

Did you update your kernel, and if yes, from what version? (Only y in 3.y is needed. Kernel options change from time to time and that's maybe some missing option(s) causes it. I have mainly NETFILTER_XT_TARGET_LOG vs. CONFIG_IP_NF_TARGET_LOG in mind. Looks like this option was changed in 3.4.)