Strange network problem

[hce <webmail.hce@gmail.com>]

Hi,

I bought a new ADSL2+ modem and connected to my debian PC. I used DHCP
to get IP address, I can ping www.google.com or any domain name, but
my browser could not see www.google.com or any web site. Any
explanations of why I could ping www.google.com (which means the DNS
and route worked fine), but the brower could not download web pages
(browser does not any problem if using other network connections)?
I've disabled all firewall and service block in the ADSL modem. My
debian system does not have any problem if connects to other network.
Could it be the modem problem?

Thank you.

Jim