I was plugging along on the internet when I decided to try the spoken commands for the first time. When I opened System Preferences and clicked on the microphone, at that instant my screen flickered and changed in both quality and what appears to be contrast and tint. I tried in vain to correct this by way of the controls for the Display in Sys. Prefs. but to no avail. I would like to know if I have a video problem or a memory problem. Any help would be greatly appreciated.