srdjanfromheidelberg: May your day rain chocolate chip cookies/brownies/your preferred alternative treat. I have been working to find a fix on this for two days now and your suggestion finally made the difference.
I started having the trackpad scroll problem Friday. Rebooting fixed it then but Saturday I completely lost trackpad scrolling ability in all apps. I tried the same things Trinli- suggests above, which I found various places online, but the problem persisted. Today I decided to give it one more try, found this thread, and voilá! Doesn't matter whether yours was just the final piece of the puzzle or the complete solution -- thank you thank you thank you!
Deets: MacBook Air purchased end of January 2014 with Mavericks already installed. Mainly I use Firefox, also fully updated. I had a similar scrolling issue on Feb 12, which I solved by unchecking all options in System Preferences/Accessibility and rebooting, per a MacForum suggestion.
I checked the FF update history and see that one was applied on March 19, the day before I started having problems. I wonder if that update undid the need to uncheck the Accessibility options. (I looked at the update details at https://www.mozilla.org/en-US/firefox/28.0/releasenotes/ but lack the technical background to understand them.)