Internet not working on Win98

Hello,
We have internet in the office through a Linksys router. All W/S are win2k except one that is win98.

For some last week win98 user could not browse the internet.
Rebooting the router and modem did not fix the problem.
I noticed that going inside DNS configuration and changing the order of DNS servers, then rebooting works. But after a while the problem appears again. As if a connection with the DNS is not being saved on win98.

Please help.
Thank you