If you are very impatient while surfing it might just be the mouse buffer catching up!
You can sometimes get these problems with wireless mice - see manufacturer's site for troubleshooting.
But if it something more sinister, try opening up the Task Manager to see what processes are running (and using resources) when that happens. Take particular note of any that are running under under your user ID. Let us know what's running and if it's safe to kill the process.
Run Ad-aware and / or Spybot.
Search Google for symptoms of the problem.
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