Pppoe-server clients can ping but no browsing etc..

[clubbing80s]

Hi
Need some help ..

I have configured the pppoe sever to listen on the private interface with the wan interface connected to a firewall that connects to the internet.

When I connected a windows xp pc to the pfs private interface and configure pppoe dialup .. Authentication works fine ..
From the xp client I can ping and traceroute to google.com ..
But I can't open any pages ..

From a windows 7 machine it works and from a linux machine it works.

I did the ping test to figure out the mtu , ping -f -l 1380 www.google.com … was where I ended up with a clear ping .

But still no browsing ...

How do I go about resolving this ?