connecting WIN98SE via Linux firewall to internet

I am sure, I am not the only one who has this strange problem!

I use an old PC as firewall whith SuSE linux 9.1 as OS. The connection
between this linux box and other internal PC's is fine. When connecting my
Win98SE box to the internet, some sites can be found with there internet
names, others not.Connecting to the pages with use of IP addresses works
always well, where names failed to do so.
Some external DNS servers are signed to the interface. So the WIN98SE box
should know where to look.
The firewall is not filtering on names and IP-addresses.
A third PC, with OS linux, is also connected behind the same firewall and
has no problems finding internet names.
It seems to mee that the Win98SE box gets only a part of data of external
DNS.

What is wrong set to my system?
--
Henk Weebers