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I can't seem to pinpoint a specific cause for this, but sometimes when I wake my MBP the external screen gets fuzzy, like a TV with no reception, but I can faintly see my desktop behind the noise. If I sleep the display again (with hot corners) and wake it up again it's fine. Anyone know how to fix this?

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@Phil What connector/adapter/cable are you using to connect your MacBook Pro to the monitor? What kind of monitor is it? How old is your MacBook Pro? –  CajunLuke Jun 1 '11 at 17:32
I have the same problem with an Acer LCD display connected via HDMI over Mini-DP to a circa 2010 MBPro 15". –  Ian C. Jun 1 '11 at 18:44
@Phil does OS X let you change the refresh rate for the display (System Preferences-> Displays)? If so, what's it set at? –  Nathan Greenstein Jun 2 '11 at 0:02
I have the same problem -- I'm using an Acer monitor that has a handful of inputs (HDMI, VGA, DVI) allowing it to basically act like a TV if one were so inclined. What seems to happen is after my MBP goes to sleep the monitor starts searching for a signal (before it turns itself off) and ends up on HDMI with no signal (hence the snow). I don't have the problem with seeing my desktop faintly, but I've seen this on other multiple input displays, including my TV -- I believe that this can be chalked up to 'cross talk'. –  John Carter Jun 2 '11 at 2:47
FWIW turning my Acer monitor off and then back on again fixes. No need to sleep the Mac. –  Ian C. Jun 2 '11 at 3:17

2 Answers 2

Since the mac engages the graphics card with the same precision each time you wake from sleep, it's likely a timing issue on the monitor. (I loose or noisy cable could have the same effect, but much less likely and you would probably have other issues if that were he case)

Have you seen if you can reduce the number of settings the monitor has to scan on detecting a new signal.

You can test this by power cycling the monitor the next time it happens.

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This happens to me with an external monitor connected via HDMI. I've found that it usually resolves itself by removing the DP -> HDMI adapter and re-plugging it in again.

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