Win98 PC visible on network, but can't use the DSL modem

The other computers can see it, and it can see the other computers.
File sharing works.

BUT: If I start a browser and try a web site, whatever program I am
using gets an "Illegal Operation" message.

What I have done so far:
Took out the Dial-Up card and NIC, uninstalled everything on the
"Network" window, so that it was empty, then put back only the NIC,
re-installed it, so that now the only things in the Network Window
were:
Client for Microsoft Networks
Linksys LNE100TX(v5)Fast Ethernet Adapter
TCP/IP

That is, just the stuff that installed spontaneously along with the
NIC, and then of course after I enabled print sharing, "File and print
sharing for Microsoft Networks" appeared.

All that had the effect of making it so it did not stall for an
abnormally long time after clicking "OK" when the "Enter Network
Password" screen comes up. Also, before I did all the above, it
crashed about half the time when clicking the aforementioned OK
button. Seems to be better now.

BUT the problem remains: The thing still can't use the DSL modem. I am
using a D-Link 624 router, if that is of any relevance.
Any help would be greatly appreciated!
-plh

--
I keep hitting "Esc" -- but I'm still here!
[if "123" is in email address, that is an anti-spam thing.]