Different Google results in FF vs IE (not signed in to Google)

I just noticed that for many search terms, I'm getting different results in Google in Firefox vs IE.

I'm not signed in to Google in either case.

I just phoned a friend who lives nearby and got him to run the same search as me in both browsers (he was not signed in to Google either). His results in IE were the same as in FF, but they did not match what I got in either of the two browsers. So there are 3 different sets of results for the same search.

I ran the same search over & over in both browsers and the results don't change each time I run the same search in the same browser; they only differ from one browser to the other.

Any ideas why this is happening?

SERPs are different for lots of different people, depending on many things such as cookies, google account, geographical region and yes even sometimes browser (i've noticed this last one rarely)

Theres a great firefox plugin @ yoast that disables personalized results in the firefox search bar. I have all of his custom searches installed in my firefox and use them nearly every day.

i have also noticed this, the other possibility is you have some form of virus or spyware/adware that is playing with your results. i had this problem not so long ago with IE.