Just installed Firefox 4 a week ago. Now, everytime it launches I have this strange display pattern that looks like a checkerboard of light and dark pixels. First I tried isolating my add-ons/plug-ins one by one, but that didn't solve the problem. Then I disabled ALL of the addons under the HELP menu and, after restart, the checkerboard pattern disappeared... but all my addons were obviously disabled. I'd like to continue to use my addons but not if this problem continues. Should I return to Firefox 3.8? I didn't have this problem with that version.