After observing this for a number of weeks and unless I'm completely in left field, Google results are platform Dependant.
[edit - added]
So here I am going to present two screenshots search term used is “sports”, one from my Mac Powerbookng Firefox.0.4 and one from my Windows based Dell Lattitudetop using Firefox.0.4 - as you can see for a number of terms Googlep roducing very different SERPS based on the operating system of the client machine.
I am not technically competent enough to judge this one, perhaps someone with the knowledge can chip in. Cornwall [/edit]