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If this is not the problem, it could be caused by your local DNS server... but I doubt it.
To see the IP that your system finds for google.com, go to a command prompt and type "ping google.com"
Also... make sure your system wasn't hijacked by a Browser Helper Object (BHO). Run BHOdemon, and remove or disable anything unfamiliar. AdAware or SpyBot Search and Destroy are good tools also.
Good luck. I hope this helps.
Regards,
R.