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fixed!

This was very annoying for me too and this is my first post and i thought, lets reply to this.... i use excel and just switched from pc to mac and got the magic mouse as well.... i tried the following below and i was good to go

FROM: http://discussions.apple.com/thread.jspa?threadID=2292349&tstart=1

To turn horizontal scrolling off:
defaults write com.apple.driver.AppleBluetoothMultitouch.mouse MouseHorizontalScroll -bool NO

To turn horizontal scrolling on:
defaults write com.apple.driver.AppleBluetoothMultitouch.mouse MouseHorizontalScroll -bool YES

These commands are entered on the command line of the Terminal utility application.

NOTE: You'll have to restart your computer before the changes take effect.
 
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