web doesnt work but email does - many trblshootng steps done

have win98 machine behind linksys router using cable modem. one PC on LAN
works fine, but another doesnt. it sends/receives email using OE jsut fine
using mailservers' names (NOT ip addr), but cant resolve websites. can ping
IP addresses on Internet, but FQDNs are intermittent. nothig in hosts or
lmhosts files, all tcp/ip info is dhcp, flushed DNS by winipcfg
release/renew, reinstalled tcp/ip, did browser repair, tried using different
browser, connected PC directly to cable modem -- none worked. swapped in
other PC and works fine, so that eliminates router port and ethernet cable
problems. bought brand-new NIC and installed in case it was the old NIC
having problems routing DNS stuff - still didnt work! two things: 1) ISP
said email works over different protocol (than TCP/IP!?) so thats why it
still worked, but doesnt explain successful use of mailservers' FQDN. 2)
maybe traffic analysis on bad PC to see whats sent or not? soon will try OS
repair/reinstall...