Cannot find DNS Server….

I have a new machine with 98b installed on it. It has Explorer 5.x and outlook express. I hooked up to my ISP and everything worked fine. The machine accidentally was shut off and now when I click on Explorer or Outlook, it dials up connects properly then stops and displays… Cannot find DNS server. ALL my TCP/IP settings are correct as before. What can my problem be and how can I correct it?
Thank you
Merv