[CentOS] DSL battling rojter - help!

My internet connection is through a Siemens Speedstream 4100 DSL modem
connected to AT&T (sbcglobal.net), and a Dlink WBR-2310 router.

Late last night, I changed the administrative password on the router,
and for some reason it didn't take right, so I had to reset the router
to get the password cleared.  Unfortunately, this also lost all my
connection settings to the DSL, and I lost the internet for a while.

After some effort and a couple of phone calls to AT&T technical
support, I determined the following:

1. If I connect my CentOS (main) box to the DSL modem, I can log into
the modem and check all the settings, and I can ping sites on the web
from there, but I can't actually get any web pages to load.  This is
using Firefox 3.6.4 (the L&G).

2. If I connect a WinXP box to the modem, it gets to the web without
any trouble.

3. If I connect the router to the modem and run the machines through
the router, no one gets to the web.  I managed to get it to a point
where I could acquire an IP address, but nothing on the web was
visible.

I'll figure out the router problem one way or another, but it really
concerns me that I couldn't get to the web from my CentOS box at all.

Before the router password fiasco, everything was working absolutely
perfectly, and I did not change ANY settings on my machines.

Now, I do have a line in /etc/hosts that sets my machine id, and its
IP address to 192.168.0.100, which is what it normally should be for
access through the router as it is the primary machine on it.  (I need
that because my VMWare SMB is set up to use that for connections
between my virtual XP machine and my CentOS host.)  Could that be the
problem with internet access directly through the DSL modem?  If so,
how do I change this to ensure that the hostname is set properly but
the IP address matches whatever the DSL modem gives back?  How do I
then also ensure that the hostname and address are set right so my
host-VMWare samba connection still work?

Otherwise, what?

Thanks.

Mark