Just as an FYI for your debugging.....both iptables commands work OK on my fork with ipset 6.
EDIT: One thing you may want to try is manually loading some of the modules if you aren't already doing so....
Code:for module in ip_set ip_set_hash_net ip_set_hash_ip xt_set do insmod $module done
I need to see if maybe xt_set might also be requiring an alias, like the various hash modules needed for the automagic module loader to work properly.