cvasil,
I don't have -i and -d switches in my iptables command, I don't think that they are necessary unless you have some complicated ip address scheeme in your machine.
Anyway, if 1.2.8 works, there should be no reason for rc7 not to work, so there must be nothing wrong with your firewall configuration.
The relevant port when it comes to lowid/highid is aMule TCP port. Once aMule is running, do:
$ netstat -nlt
$ lsof | grep amule | grep IPv4
And paste the result of these commands here, ok? Also check if you have IPFilter active on rc7.
Cheers!