I had this happen to me as well. just last week (july 28, 2014) I brought my magic mouse from home to work since my work mouse was going south. paired it with bluetooth, it moved and clicked but no scroll or gestures. searched till I nearly ready to give up. then I installed USB overdrive. many forum posts said too remove that. I didn't have it, so I installed it. and then un-installed it. everything works great now.
hope this helps someone.