Could you explain your previous setup a bit more ... do you mean a hub or a router ? If a hub, were you using Internet Connection Sharing ?
What IPs do the computers have ? The DG834G is defaulted on the 192.168.0.1 series. I think the computers probably have fixed IPs and the wrong IPs for the defaults in the DG834G, in the wrong series .... they must be in the 192.168.0.2 to 192.168.0.255 series with DHCP disabled in the router.