FC12 , DNS Problems

[Jim]

FC12/KDE
I'm having DNS problems.

I can't get Firefox to goto linuxtoday.com , lxer.com , or rpmfusion.org ,
but I can goto yahoo.com , foxnews.com .

I have to do in Firefox a about:config and inject "network.dns.disableIPv6"
to get all websites.

I can't use Konqueror WebBrowser  and goto linuxtoday.com , lxer.com , 
or rpmfusion.org,
But I can goto yahoo.com , foxnews.com .

Doing a http://www. doesn't make any difference in both browsers.

I have to make a /etc/dhclient-eth0.conf file and put
" prepend domain-name-servers 127.0.0.1; " to get Konqueror Webbrowser 
to goto all Websites.

I have two other FC12 boxes on this local network and have no problems 
like this.

What is the problem in FC12 ?