Weird one. Running Safari under OSX 10.9, I was browsing the store jumping back and forth through the various offerings when it stopped scrolling. That is, trying to scroll down on the web page either by two-finger getsures on the trackpad or clicking in the scroll bar box on the right of the window did not work, Instead of scrolling the page, it moved the navigation bar up and down (the navigation bar that contains Tips, Support, Live, etc). I tried taking a picture of the Safari window with Grab, but was told that it wasn’t allowed. Instead, I took a snapshot of a portion of the window (attached). You can see the navigation bar is located in the center of the page instead of at the top, and although you can’t see it in the screen shot, scrolling moves it (instead of the page) up and down. Starting a new window works fine, so I’m not sure how repeatable this is.