getting left-right swipe on magic mouse triggering browser back button again?

since Lion I haven't worked out how to get the get the left-right swipe on magic mouse triggering browser back button again? I found this very useful.

Anyone know how?

That is, when in a browser, previously I could swipe left on the magic mouse to go back...for swipe to right to go forward

I have a magic mouse & Lion

I just run one finger left to right on the mouse & the previous page shows up

funnily enough it now works for me.....not sure what I did....I think I did change an accessibility setting recently to get the CONTROL-MouseScollWheel zoom working..