Comment 3 for bug 297890

I have the same problem. The white flash stays, so the screen goes all white. Cheese doesn't freeze.. it just paints the screen all white. Doesn't react on alt+f4, though, because the white area takes focus. Alt+tab shows the window switcher but is unable to switch away from the white area.

There are two workarounds:

1) Switch to a different workspace and open a terminal to do killall cheese. The picture will be saved.
2) Press [space] instead of using the mouse. The flash works fine when you don't use the mouse to click Take Photo.

Others having the same problem:

http://ubuntuforums.org/showthread.php?t=943314
http://ubuntuforums.org/showthread.php?p=6321379

My webcam uses the gspca_ov519 module. My desktop effects are on default settings. Please tell me what else you need.