problem pinging my ip address

i cannot ping my own ip address, but can ping the ip addresses on the net, and on the lan, i can ping 127.0.0.1. I do not have a firewall on the lan, but windows xp firewall is on the adsl connection. I am trying to set up a network of 2 computers (i have done this successfully many many times) and am stumped. The Windows XP machine does not let me get into view workgroup computers (cannot access mshome), and the windows 98 machine will sometimes show 1 computer, sometimes 2 computer (but wont allow me to access the other machine), and sometimes nothing. I can, however, access the internet sharing facility from the windows 98 computer so they can both use the broadband connected to the XP machine. The router im using is a simple 5 port hub with no settings to change. I have re-installed the network cards on both machines, and all network stuff on the 98 machine. Anyone got any ideas as im stumped!!!!!!!