White square on screen
 

I just noticed tonight that there is a small white square in the lower left quadrant of my screen. Any window or app dragged over there still shows the square, but when I put the mouse pointer over it, it disappears. I don't know if a recent update did this. Here are some screenshots:

http://i42.photobucket.com/albums/e3...reenshot-2.png
http://i42.photobucket.com/albums/e3...reenshot-1.png
http://i42.photobucket.com/albums/e3...Screenshot.png

Interesting.
 

Is this on all the user display's?

i would start the terminal and cd into your desktop dir and ls -a (shows hidden files too) and see if there are any odd files.

EDIT: I'm guessing you can't click it.

Is it completely stationary? -- Can you move it?

Have you rebooted or, better, restarted X, did it survive?

Well ?