Try this link for several related issues:

http://www.microsoft.com/windows/IE/community/columns/IEtopten.mspx

You may be experiencing the same issue I had.  I am on COX cable HSI and was using a Toshiba modem that was about 4 years old.  Apparently Cox has upgraded their system and older modems can't handle the way data is sent.  I got a new Motorola modem (SB5120) and so far the I have not had the slow page load or the DNS message.  Would have been nice if Cox had let their customers know!