DNS issue

[robertlaferla at comcast.net (Robert La Ferla)]

Ever since I upgraded to MaraDNS (on Linux server), I've been getting 
the error message below from Firefox 1.5 (Windows client).  The error 
does not happen everytime but once in a while (consistently that is).

What could be the problem? 


HOST is whatever the host name is of the web site I tried to access.  
e.g.  en.wikipedia.org

Server not found

Firefox can't find the server at HOST

    *   Check the address for typing errors such as
          ww.example.com instead of
          www.example.com

    *   If you are unable to load any pages, check your computer's network
          connection.

    *   If your computer or network is protected by a firewall or proxy, 
make sure
          that Firefox is permitted to access the Web.