Hi, I've updated my video card (Radeon 4870) on my 2009 Mac Pro this summer, and I installed the radeon 5870HD. This happened during the Lion upgrade, so the problem that I'm experiencing is hard to assig it to Lion or the card upgrade. Here's my problem : Some of the screen savers even the ones from apple, they are showed with a black box around some of the animation ex: Arabesque, RSS Visualizer, Word of the Day, Lion Galaxy. Even the application Mach Desktop show the same corruption when browsing some of the Quartz compositions. The issue is also present in iMovie. When I browse the text effects, all of them show the black boxes and it is impossible to apply a text. What I will try to do today is to put back the old video card to check if it is hardware related. If that's the case, I know that I will try to get my card fixed or replaced. If the issue still present after swapping the cards, I don't know what can cause this issue. That's why I post now here my issue, if one of you may have experienced a similar case your help will be very welcome. I don't want to reinstall Lion and I did created a new account to check if the problem is user related or not and the new user created had the same issue. So I just hope it is hardware (video card only) related. But please if you have a hint to share please do it. Thanks for your help in advance. I will try to post some screen captures of the corruptions later this afternoon.