I tried to compile a list of everything that works on this in order of likelihood of success:
1) virus / worm
unwise.exe, a phony Windows Antivirus program, and a rootkit named tdss may have caused this problem.
run gmer, combofix, and malwarebytes to clean the computer up.
2) Uuninstall Norton products with symantec removal tool (an old symantec install may have left deviant code.) Norton may have bits and pieces left on teh disk, use Norton Removal Tool at http://service1.symantec.com/Support/tsgeninfo.nsf/docid/2005033108162039
to get EVERYTHING. McAfee, Trend Micro, and Zone Alarm have all been causes of this proble, seemingly due to a conflict with a windows update. Using approrpaite uninstallers or teh Add/Remove Programs Control Panel, you may want to uninstall your Anti-Malware entirely; disabling alone may not be adequate.
3) Try to 'telnet google.com 80', 'ipconfig /renew' from the command line, or right click the connection icon and select "Repair".
If either of those give you a weird error, then it's probably winsock corruption (Which only affects TCP, so i.e.: PING works (IP only), but a TCP connection does not)
Run winsockfix or follow directions at: http://support.microsoft.com/kb/811259
4) The Cisco VPN client has sabotaged browsing in one case. If you use it, reinstalling it may help.
5) Replace hosts.ini with only 127.0.0.1 as an entry.
6) Ensure no proxies have been set if you don't have any. In internet explorer, click tools > internet options. Then click connections and LAN settings. Remove the checkbox for 'use a proxy server'.
7) Revert to an older driver (or upgrade to another.) You may need to run winsockfix again
8) Set BIOS to defaults to undo any overclocking
9) At cmd prompt, type: ipconfig /flushdns