You either need to run ICS on one computer and connect the other to it or get a router.
Your problem is that the isp gives only 1 ip address. The switch hub doesnt have a dhcp server in it so no new ip address can be given out, hence only one computer will connect at one time.
Get a cable/dsl router, connect the dsl modem into the wan port and then connect each computer into one of the other ports. The router will assign each computer its own ip address. You may need to run the home network wizard again to set up the network but the internet should work ok.
Hope this helps out.