Every time you move with any arrow key in a text field in Safari, you hear a click, sometimes a double click. This doesn't interrupt anything, but it can get annoying to listen to constantly.
Bug First Encountered
How often the bug occurs
I have sometimes encountered this too, though not all the time. In addition, if the VO sounds are turned off by going to the VO Utility, the clicks aren't heard at all.
I've just been used to it by now. I think I reported this during the public beta when I was doing that. No fix.