found the unreal-ircd problem

SSIA -- the "Address family not supported" error when starting internal was 
caused by unreal-ircd assuming ipv6 was up (and it wasn't because we don't 
use it).
Autoloading of the module was broken because "alias net-pf-10 ipv6" was 
missing in modprobe.conf (which is why it worked elsewhere).

Short story: internal is back ;)