I have come across an issue where I was having scrolling issues after upgrading to OS X Mavericks within Web Browsers and I had to close and re-open the app to get scrolling back but it would only work for some time.
The only work around that I can find is to activate scroll bars to always be visible within apps. This may not look great, but it fixes the issue and here is how you can turn it on;
You can activate this option in System Preferences -> General -> and under “Show scroll bars” choose “Always”.