Every time I try to change the inside port IP, it fails. Nothing it written tot he ASA. I can change the outside from DHCP to any IP, but when I change the default 192.168.1.1 to my 172.20 .x.x scheme, nothing. Just the spinning cursor and the error box of death. I'm not sure the unit it working properly.
It's very likely that this problem is just an ASDM-problem. Configure it from the CLI and it will work.