Dual Monitor Problem - Flashing Black Line (ATI Radeon Sapphire HD5450)

I have a 22 inch widescreen and a 19 inch box monitor connected via DVI and VGA cables to an ATI Sapphire HD5450 graphics card. When I choose to extend the desktop onto the box monitor, I have a flashing black line on the screen. This only seems to appear while I'm using the computer - at idle it is a clear screen. I have duplicated the screen and there isn't a problem - only when I extend the desktop from monitor 1 to monitor 2. Anyone know how I can fix this?
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  1. hm... dont know if this will work
    but you can try going to catalyst control and disable overdrive if it is enabled
    just uncheck the box by the overdrive
    good luck! :D
  2. Thanks for your reply, tomate2.

    You hit the nail on the head. Worked like a charm!
  3. tomate2 said:
    hm... dont know if this will work
    but you can try going to catalyst control and disable overdrive if it is enabled
    just uncheck the box by the overdrive
    good luck! :D

    I had this problem today, same card (2nd day of using it on a dual monitor), but I'd not touched overdrive. However, after reading this I selected 'default' in CCC settings (couldn't see a 'disable overdrive' option) and...
    IT WORKED.

    Great tip thanks. My guess is that when I increased the refresh rate from 60 to 75Hz on one of the monitors it must have triggered an overdrive function and didn't reset it when I reverted to 60Hz.
  4. wow guys! it is rely working! thanks!
  5. This works but what if I want to use overdrive? Not a very good solution... thanks anyway.
  6. willpatt89 said:
    This works but what if I want to use overdrive? Not a very good solution... thanks anyway.


    The problem will return once you start a game or any heavy video. This video card don't like VGA, just used HDMI and DVI cable to monitor and you good.
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