We have seen a large number of computers coming in with problems navigation on the internet.
Also unable to go to Windows update and viurs update sites. Here is a quick fix that also seems to speed navigation up some.
Just for safety create a copy of the file before making changes.
C:\windows\system32\drivers\etc\ (Windows XP)
C:\I386 (Windows 2000)
Open the host with notepad.
remove all entries bellow
then save and close