6 Replies Latest reply: Mar 29, 2011 7:30 AM by Grant Bennet-Alder
Jiri Mihal Level 1 (0 points)
Flickering computer screen, after flickerign turns to black and then whole computer freez. When computer freez, sound goes without problems, mouse or keyboard work but can't control applications. I did HW test on start-up, no problem was found. Please help. Thank you!

You can see posterize effect on backgroung when screen is flickering:

MacPro2008, Mac OS X (10.5.8), 2x3Ghz, 4GB800Mhz RAM, NVIDIA GeForce 8800 GT
  • David Heywood Wilkinson Level 1 (10 points)
    I am having a similar problem. Weird artifacts are showing on the screen, as well as occasional flickering. Prone to freezing up after waking - keyboard and mouse unresponsive. Hard Restart is needed. The problem started a week ago when the computer would wake from sleep in a frozen state. Yesterday and today the screen went completely fuzzy (like old tv static).

    Yesterday I wided my drive and reinstalled Snow Leopard. Problem appeared immediately. Tried a second drive today and but the problem is still present. I tested the RAM using Rember, but no errors were found. I ran the Apple Hardware Test several times and no errors were found. Any thoughts or feedback from the Apple community would be greatly welcomed.
  • Ben Blaine Level 1 (5 points)
    I'm suffering from the same problem. Odd screen artefacts started a couple of months back but I ignored them as I thought I just had cheap monitors...

    But then for the past week I've had a system freeze just like what you're both describing. Looking into it I think it might be a problem with the graphics card... I'm still on the ATI Radeon X1900 XT... Does anyone out there know if getting a new card could sort out the problem? If so what card would you recommend?

    best wishes.
  • joemaurice Level 1 (15 points)
    Hi there is a HUGE thread on this here:


    Has a fix on page 28 for those with ATI cards. I have tried to do similar with NVIDIA card but with mixed results. If I work it out i will post my solution but its not perfect.

    remember to post to Apple support so they are aware of the problem.
  • The hatter Level 9 (60,930 points)
    There is a recall for some serial number series of X1900s.

    Dust and heat has always been an issue with that card needing to be pulled and cleaned every 3 months or so. Real dust magnet.

    There is only ONE card sold, ATI 5770 $249 requirement is any Mac Pro with 10.6.5 or later.
  • David Heywood Wilkinson Level 1 (10 points)

    I installed the 5770 in my late model Mac Pro, and it definitely has some benefits and drawbacks. The benefits include the 1GB of VRAM, which really shines in Photoshop. Also, I see less stutter and lag on flash-heavy websites.

    The con, however, are pretty disappointing. My mouse jumps around the screen when I plug in two displays using the DVI port and the mini-DisplayPort with a DVI connection. The mouse is simply unusable. I can remedy the problem by using a VGA connection with the mini-DisplayPort, but it seems off that I would need to go analog.
  • Grant Bennet-Alder Level 9 (56,679 points)
    Has a fix on page 28 for those with ATI cards.

    I think that would be the procedure to replace the ATI drivers with the ones from 10.6.2, using the Terminal procedure specified at this link: