Did the same thing, with one Win98 machine that gave me fits, crashing so completely I had to get into the BIOS to reload Windows to recover. The XP machines were a snap.
The network set up without a hitch ( Asante router, Westell Wirespeed 2100 DSL modem, Win2K on both machines ) other than fiddling with the connection tabs-- all the default settings are fine. Only problem is, Ebay hangs when I try to go there. It did that with the un-networked main PC whenever I had Kerio's software firewall running. Disable Kerio, it opened Ebay fine.
The router has a built-in hardware firewall, so I am assuming it is a similar problem with the firewall there. I posed the problem to Asante's forum, so maybe someone there has an answer.
I normally avoid Ebay, but am checking on a bag phone there- I can, of course, just straightwire the modem to the main PC and proceed, but that's a little cumbersome to keep doing.
Two options I have not yet tried are running the router's installation CD, or going into the router via the browser ( like you do a DSL modem ) and looking at its internal settings to see if everything looks Kosher.