Has this ever happened to you?
I'm not sure what combination of buttons I pushed but now when ever my cursor lands over a photo, a window pops up next to the cursor. Whenever I go over to a new photo the same viewer pops up for that photo then as well.
That's the image tooltip window. to turn it on and off hit the control and T keys. Once for on and then again for off. See Displaying Metadata with Your Images for more information.