It's the one really annoying thing in Mavericks, aside from Launchpad (which it appears I'm too late to complain about, since I skipped over Lion and Mountain Lion).
The problem is, scrolling will periodically stop working with the magic mouse in Firefox. Here's how to fix it. First of all, deactivate this crap in the control panel:
Now, get yourself BetterTouchTool and set it up like this:
The first two entries are the important ones. The rest are my personal preferences. Setting up the paging forward and back with two fingers here rather than in the OS X control panel fixes the problem. No more restarting the browser and cursing. Happy scrolling!