Lost on Home Network

I currently have 3 computers a home and have had others. I’ve never had a problem connecting them to the internet. I built a comptuer, all is fine exept I can’t get online. Device Manager says everything is fine. IP address is fine. I’ve enabled connection sharing and made sure all was well with all configurations. What am I doing wrong? The other 2 computers are online and my hub shows a connection being made, LAN card shows fine. My cable service provider says they don’t understand what the problem could be. Can anyone help?
I’m on Windows 98, system board is Tyan s1584, card is Dlink, 733MHz, 133 FSB, 256mb ram, the only jumpers explained I believe are positioned correctly.