Whenever I edit an answer (not a question, it seems), I see a giant cursor on the side that only disappears when I force the cursor somewhere else. It's difficult to show because it blinks.
It also appears when I click the buttons at the top, but miss.
And because you'll ask,
Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.2) Gecko/20100115 Firefox/3.6 (.NET CLR 3.5.30729)