Black artifacts flickering at bottom of window when scrolling up or down. It is a black bar with no content, sometimes occupying 30% of bottom part of window. However, Microsoft offered an emergency fix-it for IE on September 20, 2012. This problem went away for few hours. Installing the critical update for IE allowed FF to run without this issue for two days after install on September 23rd. Why that would be, I cannot say. Have a screenshot of FF when this happens. Bar is very small ATM, but flickers just the same. Normal artifact extends from left side to right side; only a partial bar is caught with this screenshot. Where to attach screenshot?