There's a bug in Opera where I use an <input type=file /> element(control) to have the client select a file from his local storage device and in my FileReader.onloadend event handler I set the result to an img.src property on the page. Everything works but until you move the mouse the blue circling arrow animation stays on the screen. It's misleading, so I classify it as a bug.
EDITED: Hmmm, seems to be working properly now. Maybe something else unrelated was going on. I don't know.