My Mac has started flashing the screen instead of beeping. It's exactly the same effect as you'd get if the Accessibility pref pane's "flash the screen" option was enabled, except that it's not enabled.
I also verified that the preferences property list file affecting this setting shows it as being off. In
~/Library/Preferences/com.apple.universalaccess.plist I see:
In case it makes any difference, the system sound is otherwise normal and not muted. I'm listening to music from iTunes, but getting screen flashes instead of beeps.
This happened a couple of weeks ago, and rebooting the Mac got things back to normal. Why does it keep happening? Is there something I can do to stop it from repeating again? The screen flash is going to give me a seizure.