My guess is that the 192.168.0.x network you're using for the Dell and your other machines to access the internet is the same network that ICS wants to use. Change your normal internal network to use something else, like 192.168.1.x, and see if that helps.

Chances are that your router is using DHCP to hand out the addresses to your normally connected computers, so you'll probably have to modify its configuration to get the network to change. Assuming, of course, that your router allows you to change that network.

ICS might also allow you to change the network it uses, but I've got no idea how to do it even if it is possible, which it may well not be. (Although that ``Settings...'' button looks promising.)