Technical details:
The databases used by some DNS servers occasionally become corrupt, or are misconfigured, causing two hostnames to redirect to the same IP address. When this occurs, you may type an address (URL) into the browser, and the browser may take you to the wrong web site. After this occurs, IE will keep these incorrect web site pages in its cache ("Temporary Internet Files") for hours or days, even after the DNS corruption is fixed.
This situation has been known to happen with older DNS servers that get overloaded, or run out of memory to store DNS entries. This problem can be exacerbated by a wave of viruses which perform a large number of DNS lookups.
Correcting the Problem
If you are still having problems, you can
You may also need to inform the ISP of the problem, and ask them to reboot their DNS server, or at least flush its cache. Otherwise the problem will re-occur.
Clearing the Temporary Internet Files
To clear the Internet Explorer cache, do one of the following:
C:\> ipconfig /displaydns > "%USERPROFILE%\Desktop\GatorDNS.txt"
http://support.microsoft.com:80/support/kb/articles/Q245/4/37.ASP